# migrations

dir: embeddings_queue
filename: 00001-embeddings.sqlite.sql
hash: d3755dfd232be8e8301f4d7fcfb3a486
sql:
CREATE TABLE embeddings_queue (
    seq_id INTEGER PRIMARY KEY,
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    operation INTEGER NOT NULL,
    topic TEXT NOT NULL,
    id TEXT NOT NULL,
    vector BLOB,
    encoding TEXT,
    metadata TEXT
);


dir: sysdb
filename: 00001-collections.sqlite.sql
hash: 38352d725ad1c16074fac420b22b4633
sql:
CREATE TABLE collections (
    id TEXT PRIMARY KEY,
    name TEXT NOT NULL,
    topic TEXT NOT NULL,
    UNIQUE (name)
);

CREATE TABLE collection_metadata (
    collection_id TEXT REFERENCES collections(id) ON DELETE CASCADE,
    key TEXT NOT NULL,
    str_value TEXT,
    int_value INTEGER,
    float_value REAL,
    PRIMARY KEY (collection_id, key)
);


dir: sysdb
filename: 00002-segments.sqlite.sql
hash: 2913cb6a503055a95f625448037e8912
sql:
CREATE TABLE segments (
    id TEXT PRIMARY KEY,
    type TEXT NOT NULL,
    scope TEXT NOT NULL,
    topic TEXT,
    collection TEXT REFERENCES collection(id)
);

CREATE TABLE segment_metadata (
    segment_id TEXT  REFERENCES segments(id) ON DELETE CASCADE,
    key TEXT NOT NULL,
    str_value TEXT,
    int_value INTEGER,
    float_value REAL,
    PRIMARY KEY (segment_id, key)
);


dir: sysdb
filename: 00004-tenants-databases.sqlite.sql
hash: 048867ce8fcdefe4023c7110e4433591
sql:
CREATE TABLE IF NOT EXISTS tenants (
    id TEXT PRIMARY KEY,
    UNIQUE (id)
);

CREATE TABLE IF NOT EXISTS databases (
    id TEXT PRIMARY KEY, -- unique globally
    name TEXT NOT NULL, -- unique per tenant
    tenant_id TEXT NOT NULL REFERENCES tenants(id) ON DELETE CASCADE,
    UNIQUE (tenant_id, name) -- Ensure that a tenant has only one database with a given name
);

CREATE TABLE IF NOT EXISTS collections_tmp (
    id TEXT PRIMARY KEY, -- unique globally
    name TEXT NOT NULL, -- unique per database
    topic TEXT NOT NULL,
    dimension INTEGER,
    database_id TEXT NOT NULL REFERENCES databases(id) ON DELETE CASCADE,
    UNIQUE (name, database_id)
);

-- Create default tenant and database
INSERT OR REPLACE INTO tenants (id) VALUES ('default_tenant'); -- The default tenant id is 'default_tenant' others are UUIDs
INSERT OR REPLACE INTO databases (id, name, tenant_id) VALUES ('00000000-0000-0000-0000-000000000000', 'default_database', 'default_tenant');

INSERT OR REPLACE INTO collections_tmp (id, name, topic, dimension, database_id)
    SELECT id, name, topic, dimension, '00000000-0000-0000-0000-000000000000' FROM collections;
DROP TABLE collections;
ALTER TABLE collections_tmp RENAME TO collections;


dir: sysdb
filename: 00005-remove-topic.sqlite.sql
hash: b1367c826b8fba5f96f27befdc1d42d2
sql:
-- Remove the topic column from the Collections and Segments tables

ALTER TABLE collections DROP COLUMN topic;
ALTER TABLE segments DROP COLUMN topic;


dir: sysdb
filename: 00006-collection-segment-metadata.sqlite.sql
hash: 4eea7468935bf25d4604a0fed2366116
sql:
-- SQLite does not support adding check with alter table, as a result, adding a check
-- involve creating a new table and copying the data over. It is over kill with adding
-- a boolean type column. The application write to the table needs to ensure the data
-- integrity.
ALTER TABLE collection_metadata ADD COLUMN bool_value INTEGER;
ALTER TABLE segment_metadata ADD COLUMN bool_value INTEGER;


dir: sysdb
filename: 00007-collection-config.sqlite.sql
hash: 1c7e63bba346a42a18b6ab7f1c989bed
sql:
-- Stores collection configuration dictionaries.
ALTER TABLE collections ADD COLUMN config_json_str TEXT;


dir: sysdb
filename: 00008-maintenance-log.sqlite.sql
hash: 0a0e7e93111a01789addf64961c6127c
sql:
-- Records when database maintenance operations are performed.
-- At time of creation, this table is only used to record vacuum operations.
CREATE TABLE maintenance_log (
  id INT PRIMARY KEY,
  timestamp INT NOT NULL,
  operation TEXT NOT NULL
);


dir: sysdb
filename: 00009-segment-collection-not-null.sqlite.sql
hash: 054355aef9e63702bf54ea29e61563f1
sql:
-- This makes segments.collection non-nullable.
CREATE TABLE segments_temp (
    id TEXT PRIMARY KEY,
    type TEXT NOT NULL,
    scope TEXT NOT NULL,
    collection TEXT REFERENCES collection(id) NOT NULL
);

INSERT INTO segments_temp SELECT * FROM segments;
DROP TABLE segments;
ALTER TABLE segments_temp RENAME TO segments;


dir: metadb
filename: 00001-embedding-metadata.sqlite.sql
hash: 2b4cf52c4bb2676e21d6860a4409f856
sql:
CREATE TABLE embeddings (
    id INTEGER PRIMARY KEY,
    segment_id TEXT NOT NULL,
    embedding_id TEXT NOT NULL,
    seq_id BLOB NOT NULL,
    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
    UNIQUE (segment_id, embedding_id)
);

CREATE TABLE embedding_metadata (
    id INTEGER REFERENCES embeddings(id),
    key TEXT NOT NULL,
    string_value TEXT,
    int_value INTEGER,
    float_value REAL,
    PRIMARY KEY (id, key)
);

CREATE TABLE max_seq_id (
    segment_id TEXT PRIMARY KEY,
    seq_id BLOB NOT NULL
);

CREATE VIRTUAL TABLE embedding_fulltext USING fts5(id, string_value);


dir: metadb
filename: 00002-embedding-metadata.sqlite.sql
hash: 12a570f7121b3a8ce750a2a7c36da20f
sql:
-- SQLite does not support adding check with alter table, as a result, adding a check
-- involve creating a new table and copying the data over. It is over kill with adding
-- a boolean type column. The application write to the table needs to ensure the data
-- integrity.
ALTER TABLE embedding_metadata ADD COLUMN bool_value INTEGER


dir: metadb
filename: 00003-full-text-tokenize.sqlite.sql
hash: f97ad6334aeaa8f419f01110b648b97a
sql:
CREATE VIRTUAL TABLE embedding_fulltext_search USING fts5(string_value, tokenize='trigram');
INSERT INTO embedding_fulltext_search (rowid, string_value) SELECT rowid, string_value FROM embedding_metadata;
DROP TABLE embedding_fulltext;


dir: metadb
filename: 00004-metadata-indices.sqlite.sql
hash: fb36603a45ee2cd0254cef3ef86585e8
sql:
CREATE INDEX IF NOT EXISTS embedding_metadata_int_value ON embedding_metadata (key, int_value) WHERE int_value IS NOT NULL;
CREATE INDEX IF NOT EXISTS embedding_metadata_float_value ON embedding_metadata (key, float_value) WHERE float_value IS NOT NULL;
CREATE INDEX IF NOT EXISTS embedding_metadata_string_value ON embedding_metadata (key, string_value) WHERE string_value IS NOT NULL;


# embeddings_queue

created_at: 2024-09-26 04:33:25
topic: persistent://default/default/f81812c1-3d1d-40de-83b4-4d1583367f4e
id: /home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf_page_0
encoding: FLOAT32
metadata:
{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 0, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "11\nC\nhapter\nSSSSS\nOOOOOUUUUUNNNNNDDDDD\nEveryday we hear sounds from various\nsources like humans, birds, bells, machines,\nvehicles, televisions, radios etc. Sound is a\nform of energy which produces a sensation\nof hearing in our ears. There are also other\nforms of energy like mechanical energy, light\nenergy, etc. We have talked about mechanical\nenergy in the previous chapters. You have\nbeen taught about conservation of energy,\nwhich states that we can neither create nor\ndestroy energy. We can just change it from\none form to another. When you clap, a sound\nis produced. Can you produce sound without\nutilising your energy? Which form of energy\ndid you use to produce sound? In this\nFig. 11.1: Vibrating tuning fork just touching the\nchapter we are going to learn how sound is\nsuspended table tennis ball.\nproduced and how it is transmitted through\na medium and received by our ears.\nActivity _____________11.2\n11.1 Production of Sound\n\u2022 Fill water in a beaker or a glass up to\nthe brim. Gently touch the water surface\nActivity _____________11.1 with one of the prongs of the vibrating\ntuning fork, as shown in Fig. 11.2.\n\u2022 Take a tuning fork and set it vibrating \u2022 Next dip the prongs of the vibrating\nby striking its prong on a rubber pad. tuning fork in water, as shown in Fig.\nBring it near your ear. 11.3.\n\u2022 Do you hear any sound? \u2022 Observe what happens in both the\n\u2022 Touch one of the prongs of the vibrating cases.\ntuning fork with your finger and share \u2022 Discuss with your friends why this\nyour experience with your friends. happens.\n\u2022 Now, suspend a table tennis ball or a\nsmall plastic ball by a thread from a\nsupport [Take a big needle and a\nthread, put a knot at one end of the\nthread, and then with the help of the\nneedle pass the thread through the\nball]. Touch the ball gently with the\nprong of a vibrating tuning\nfork (Fig. 11.1).\n\u2022 Observe what happens and discuss\nwith your friends. Fig. 11.2: One of the prongs of the vibrating tuning\nfork touching the water surface.\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
topic: persistent://default/default/f81812c1-3d1d-40de-83b4-4d1583367f4e
id: /home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf_page_1
encoding: FLOAT32
metadata:
{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 1, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "the vibrating object to the ear. A particle of\nthe medium in contact with the vibrating\nobject is first displaced from its equilibrium\nposition. It then exerts a force on the adjacent\nparticle. As a result of which the adjacent\nparticle gets displaced from its position of\nrest. After displacing the adjacent particle the\nfirst particle comes back to its original\nposition. This process continues in the\nmedium till the sound reaches your ear. The\ndisturbance created by a source of sound in\nFig. 11.3: Both the prongs of the vibrating tuning the medium travels through the medium and\nfork dipped in water not the particles of the medium.\nA wave is a disturbance that moves\nFrom the above activities what do you through a medium when the particles of the\nconclude? Can you produce sound without medium set neighbouring particles into\na vibrating object? motion. They in turn produce similar motion\nIn the above activities we have produced in others. The particles of the medium do not\nsound by striking the tuning fork. We can move forward themselves, but the\nalso produce sound by plucking, scratching, disturbance is carried forward. This is what\nrubbing, blowing or shaking different objects. happens during propagation of sound in a\nAs per the above activities what do we do to medium, hence sound can be visualised as a\nthe objects? We set the objects vibrating and wave. Sound waves are characterised by the\nproduce sound. Vibration means a kind of motion of particles in the medium and are\nrapid to and fro motion of an object. The called mechanical waves.\nsound of the human voice is produced due Air is the most common medium through\nto vibrations in the vocal cords. When a bird which sound travels. When a vibrating object\nmoves forward, it pushes and compresses the\nflaps its wings, do you hear any sound? Think\nair in front of it creating a region of high\nhow the buzzing sound accompanying a bee\npressure. This region is called a compression\nis produced. A stretched rubber band when\n(C), as shown in Fig. 11.4. This compression\nplucked vibrates and produces sound. If you\nstarts to move away from the vibrating object.\nhave never done this, then do it and observe\nWhen the vibrating object moves backwards,\nthe vibration of the stretched rubber band.\nit creates a region of low pressure called\nActivity _____________11.3 rarefaction (R), as shown in Fig. 11.4. As the\nobject moves back and forth rapidly, a series\n\u2022 Make a list of different types of of compressions and rarefactions is created in\nmusical instruments and discuss the air. These make the sound wave that\nwith your friends which part of the\ninstrument vibrates to produce\nsound.\n11.2 Propagation of Sound\nSound is produced by vibrating objects. The\nmatter or substance through which sound\nis transmitted is called a medium. It can be\nsolid, liquid or gas. Sound moves through a\nmedium from the point of generation to the\nlistener. When an object vibrates, it sets the\nFig. 11.4: A vibrating object creating a series of\nparticles of the medium around it vibrating.\ncompressions (C) and rarefactions (R) in\nThe particles do not travel all the way from the medium.\n128 SCIENCE\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
topic: persistent://default/default/f81812c1-3d1d-40de-83b4-4d1583367f4e
id: /home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf_page_2
encoding: FLOAT32
metadata:
{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 2, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "propagates through the medium. The regions where the coils become closer\nCompression is the region of high pressure are called compressions (C) and the regions\nand rarefaction is the region of low pressure. where the coils are further apart are called\nPressure is related to the number of particles\nrarefactions (R). As we already know, sound\nof a medium in a given volume. More density\npropagates in the medium as a series of\nof the particles in the medium gives more\ncompressions and rarefactions. Now, we can\npressure and vice versa. Thus, propagation\ncompare the propagation of disturbance in a\nof sound can be visualised as propagation of\nslinky with the sound propagation in the\ndensity variations or pressure variations in\nmedium. These waves are called longitudinal\nthe medium.\nQ waves. In these waves the individual particles\nuestion of the medium move in a direction parallel to\nthe direction of propagation of the disturbance.\n1. How does the sound produced by The particles do not move from one place to\na vibrating object in a medium another but they simply oscillate back and\nreach your ear? forth about their position of rest. This is\n2. Explain how sound is produced exactly how a sound wave propagates, hence\nby your school bell. sound waves are longitudinal waves.\n3. Why are sound waves called There is also another type of wave, called\nmechanical waves? a transverse wave. In a transverse wave\n4. Suppose you and your friend are particles do not oscillate along the direction\non the moon. Will you be able to of wave propagation but oscillate up and down\nhear any sound produced by about their mean position as the wave travels.\nyour friend? Thus, a transverse wave is the one in which\nthe individual particles of the medium move\n11.2.1S about their mean positions in a direction\nOUND WAVES ARE LONGITUDINAL\nperpendicular to the direction of wave\nWAVES\npropagation. When we drop a pebble in a\nActivity _____________11.4 pond, the waves you see on the water surface\nis an example of transverse wave. Light is a\n\u2022 Take a slinky. Ask your friend to hold transverse wave but for light, the oscillations\none end. You hold the other end.\nare not of the medium particles or their\nNow stretch the slinky as shown in\npressure or density\u2014 it is not a mechanical\nFig. 11.5(a). Then give it a sharp push\nwave. You will come to know more about\ntowards your friend.\ntransverse waves in higher classes.\n\u2022 What do you notice? If you move your\nhand pushing and pulling the slinky\n11.2.2C\nalternatively, what will you observe? HARACTERISTICS OF A SOUND\n\u2022 If you mark a dot on the slinky, you\nWAVE\nwill observe that the dot on the slinky\nwill move back and forth parallel to We can describe a sound wave by its\nthe direction of the propagation of the \u2022 frequency\ndisturbance.\n\u2022 amplitude and\n\u2022 speed.\nA sound wave in graphic form is shown in\n(a)\nFig. 11.6(c), which represents how density and\npressure change when the sound wave moves\nin the medium. The density as well as the\npressure of the medium at a given time varies\n(b) with distance, above and below the average\nFig. 11.5: Longitudinal wave in a slinky. value of density and pressure. Fig. 11.6(a) and\nSOUND 129\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
topic: persistent://default/default/f81812c1-3d1d-40de-83b4-4d1583367f4e
id: /home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf_page_3
encoding: FLOAT32
metadata:
{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 3, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "Fig. 11.6(b) represent the density and\nHeinrich Rudolph Hertz\npressure variations, respectively, as a sound\nwas born on 22 February\nwave propagates in the medium.\n1857 in Hamburg,\nCompressions are the regions where\nGermany and educated at\nparticles are crowded together and the University of Berlin. He\nrepresented by the upper portion of the curve confirmed J.C. Maxwell\u2019s\nin Fig. 11.6(c). The peak represents the region electromagnetic theory by\nof maximum compression. Thus, his experiments. He laid the\ncompressions are regions where density as H. R. Hertz foundation for future\nwell as pressure is high. Rarefactions are the development of radio, telephone, telegraph\nregions of low pressure where particles are and even television. He also discovered the\nspread apart and are represented by the photoelectric effect which was later\nvalley, that is, the lower portion of the curve explained by Albert Einstein. The SI unit of\nfrequency was named as hertz in his honour.\nin Fig. 11.6(c). A peak is called the crest and a\nvalley is called the trough of a wave.\nThe distance between two consecutive Frequency tells us how frequently an\ncompressions (C) or two consecutive event occurs. Suppose you are beating a\nrarefactions (R) is called the wavelength, as drum. How many times you are beating the\nshown in Fig. 11.6(c), The wavelength is drum in unit time is called the frequency of\nusually represented by \u03bb (Greek letter your beating the drum. We know that when\nlambda). Its SI unit is metre (m). sound is propagated through a medium, the\nFig. 11.6: Sound propagates as density or pressure variations as shown in (a) and (b), (c) represents\ngraphically the density and pressure variations.\n130 SCIENCE\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
topic: persistent://default/default/f81812c1-3d1d-40de-83b4-4d1583367f4e
id: /home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf_page_4
encoding: FLOAT32
metadata:
{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 4, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "density of the medium oscillates between a\nmaximum value and a minimum value. The\nchange in density from the maximum value\nto the minimum value, then again to the\nmaximum value, makes one complete\noscillation. The number of such oscillations\nper unit time is the frequency of the sound\nwave. If we can count the number of the\ncompressions or rarefactions that cross us\nper unit time, we will get the frequency of\nthe sound wave. It is usually represented by\n\u03bd (Greek letter, nu). Its SI unit is hertz\n(symbol, Hz).\nThe time taken by two consecutive\ncompressions or rarefactions to cross a fixed\npoint is called the time period of the wave. In\nother words, we can say that the time taken\nfor one complete oscillation is called the time\nperiod of the sound wave. It is represented by Fig. 11.7: Low pitch sound has low frequency and\nhigh pitch of sound has high frequency.\nthe symbol T. Its SI unit is second (s).\nFrequency and time period are related as as shown in Fig. 11.6(c). For sound its unit\nfollows:\nwill be that of density or pressure.\n1\nv = The loudness or softness of a sound is\nT determined basically by its amplitude. The\namplitude of the sound wave depends upon\nA violin and a flute may both be played at\nthe force with which an object is made to\nthe same time in an orchestra. Both sounds\nvibrate. If we strike a table lightly, we hear a\ntravel through the same medium, that is, air\nsoft sound because we produce a sound wave\nand arrive at our ear at the same time. Both\nsounds travel at the same speed irrespective\nof the source. But the sounds we receive are\ndifferent. This is due to the different\ncharacteristics associated with the sound.\nPitch is one of the characteristics.\nHow the brain interprets the frequency\nof an emitted sound is called its pitch. The\nfaster the vibration of the source, the\nhigher is the frequency and the higher is\nthe pitch, as shown in Fig. 11.7. Thus, a\nhigh pitch sound corresponds to more\nnumber of compressions and rarefactions\npassing a fixed point per unit time.\nObjects of different sizes and conditions\nvibrate at different frequencies to produce\nsounds of different pitch.\nThe magnitude of the maximum\ndisturbance in the medium on either side of\nthe mean value is called the amplitude of the\nFig. 11.8: Soft sound has small amplitude and\nwave. It is usually represented by the letter A,\nlouder sound has large amplitude.\nSOUND 131\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
topic: persistent://default/default/f81812c1-3d1d-40de-83b4-4d1583367f4e
id: /home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf_page_5
encoding: FLOAT32
metadata:
{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 5, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "of less energy (amplitude). If we hit the table\nExample 11.1 A sound wave has a\nhard we hear a louder sound. Can you tell\nfrequency of 2 kHz and wave length\nwhy? A sound wave spreads out from its\n35 cm. How long will it take to travel\nsource. As it moves away from the source its 1.5 km?\namplitude as well as its loudness decreases.\nSolution:\nLouder sound can travel a larger distance as\nit is associated with higher energy. Fig. 11.8 Given,\nshows the wave shapes of a loud and a soft Frequency, \u03bd = 2 kHz = 2000 Hz\nsound of the same frequency. Wavelength, \u03bb = 35 cm = 0.35 m\nThe quality or timber of sound is that\nWe know that speed, v of the wave\ncharacteristic which enables us to distinguish\n= wavelength \u00d7 frequency\none sound from another having the same pitch\nv = \u03bb \u03bd\nand loudness. The sound which is more\n= 0.35 m 2000 Hz = 700 m/s\npleasant is said to be of a rich quality. A sound\nThe time taken by the wave to travel a\nof single frequency is called a tone. The sound\ndistance, d of 1.5 km is\nwhich is produced due to a mixture of several\nfrequencies is called a note and is pleasant to\nlisten to. Noise is unpleasant to the ear! Music\nis pleasant to hear and is of rich quality. Thus sound will take 2.1 s to travel a\nQ\ndistance of 1.5 km.\nuestions Q\nuestions\n1. Which wave property determines\n(a) loudness, (b) pitch?\n1. What are wavelength, frequency,\n2. Guess which sound has a higher\ntime period and amplitude of a\npitch: guitar or car horn?\nsound wave?\n2. How are the wavelength and\nfrequency of a sound wave\nThe speed of sound is defined as the\nrelated to its speed?\ndistance which a point on a wave, such as a\n3. Calculate the wavelength of a\ncompression or a rarefaction, travels per unit\nsound wave whose frequency is\ntime.\n220 Hz and speed is 440 m/s in\nWe know,\na given medium.\nspeed, v = distance / time\n4. A person is listening to a tone of\nl\n500 Hz sitting at a distance of\n=\nT 450 m from the source of the\nsound. What is the time interval\nHere \u03bb is the wavelength of the sound wave. It between successive compressions\nis the distance travelled by the sound wave in from the source?\none time period (T) of the wave. Thus,\nThe amount of sound energy passing each\nsecond through unit area is called the intensity\nv = \u03bb \u03bd\nof sound. We sometimes use the terms\n\u201cloudness\u201d and \u201cintensity\u201d interchangeably,\nor v = \u03bb \u03bd\nbut they are not the same. Loudness is a\nThat is, speed = wavelength \u00d7 frequency.\nmeasure of the response of the ear to the sound.\nThe speed of sound remains almost the\nEven when two sounds are of equal intensity,\nsame for all frequencies in a given medium\nwe may hear one as louder than the other\nunder the same physical conditions.\nsimply because our ear detects it better.\n132 SCIENCE\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
topic: persistent://default/default/f81812c1-3d1d-40de-83b4-4d1583367f4e
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{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 6, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "Q\nQ\nuestion\nuestion\n1. Distinguish between loudness\n1. In which of the three media, air,\nand intensity of sound.\nwater or iron, does sound travel\nthe fastest at a particular\n11.2.3S\nPEED OF SOUND IN DIFFERENT temperature?\nMEDIA\nSound propagates through a medium at a finite 11.3 Reflection of Sound\nspeed. The sound of a thunder is heard a little\nSound bounces off a solid or a liquid like a\nlater than the flash of light is seen. So, we can\nrubber ball bounces off a wall. Like light, sound\nmake out that sound travels with a speed\ngets reflected at the surface of a solid or liquid\nwhich is much less than the speed of light. The\nand follows the same laws of reflection as you\nspeed of sound depends on the properties of\nhave studied in earlier classes. The directions\nthe medium through which it travels. You will\nin which the sound is incident and is reflected\nlearn about this dependence in higher classes.\nmake equal angles with the normal to the\nThe speed of sound in a medium depends on\nreflecting surface at the point of incidence, and\ntemperature of the medium. The speed of\nthe three are in the same plane. An obstacle of\nsound decreases when we go from solid to\nlarge size which may be polished or rough is\ngaseous state. In any medium as we increase\nneeded for the reflection of sound waves.\nthe temperature, the speed of sound increases.\nFor example, the speed of sound in air is 331 Activity _____________11.5\nm s\u20131 at 0 \u00baC and 344 m s\u20131 at 22 \u00baC. The speeds\nof sound at a particular temperature in various \u2022 Take two identical pipes, as shown in\nmedia are listed in Table 11.1. You need not Fig. 11.9. You can make the pipes\nmemorise the values. using chart paper. The length of the\npipes should be sufficiently long\nas shown.\nTable 11.1: Speed of sound in\n\u2022 Arrange them on a table near a wall.\ndifferent media at 25 \u00baC\n\u2022 Keep a clock near the open end of one\nof the pipes and try to hear the sound\nState Substance Speed in m/s of the clock through the other pipe.\n\u2022 Adjust the position of the pipes so\nSolids Aluminium 6420\nthat you can best hear the sound of\nNickel 6040 the clock.\nSteel 5960 \u2022 Now, measure the angles of incidence\nand reflection and see the\nIron 5950\nrelationship between the angles.\nBrass 4700 \u2022 Lift the pipe on the right vertically\nto a small height and observe\nGlass (Flint) 3980\nwhat happens.\nLiquids Water (Sea) 1531 (In place of a clock, a mobile phone\non vibrating mode may also be used.)\nWater (distilled) 1498\nEthanol 1207\nMethanol 1103\nGases Hydrogen 1284\nHelium 965\nAir 346\nOxygen 316\nSulphur dioxide 213\nFig. 11.9: Reflection of sound\nSOUND 133\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
topic: persistent://default/default/f81812c1-3d1d-40de-83b4-4d1583367f4e
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{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 7, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "11.3.1E CHO What is the distance of the cliff from the\nperson if the speed of the sound, v is\nIf we shout or clap near a suitable reflecting\ntaken as 346 m s\u20131?\nobject such as a tall building or a\nmountain,we will hear the same sound\nSolution:\nagain a little later. This sound which we\nhear is called an echo. The sensation of Given,\nsound persists in our brain for about 0.1 Speed of sound, v = 346 m s\u20131\ns. To hear a distinct echo the time interval Time taken for hearing the echo,\nbetween the original sound and the t = 2 s\nreflected one must be at least 0.1s. If we Distance travelled by the sound\ntake the speed of sound to be 344 m/s at a\n= v \u00d7 t = 346 m s\u20131 \u00d7 2 s = 692 m\ngiven temperature, say at 22 \u00baC in air, the\nIn 2 s sound has to travel twice the\nsound must go to the obstacle and reach\ndistance between the cliff and the\nback the ear of the listener on reflection after\nperson. Hence, the distance between the\n0.1s. Hence, the total distance covered by\ncliff and the person\nthe sound from the point of generation to\n= 692 m/2 = 346 m.\nthe reflecting surface and back should be\nat least (344 m/s) \u00d7 0.1 s = 34.4 m. Thus, Q\nuestion\nfor hearing distinct echoes, the minimum\ndistance of the obstacle from the source of\n1. An echo is heard in 3 s. What is\nsound must be half of this distance, that\nthe distance of the reflecting\nis, 17.2 m. This distance will change with\nthe temperature of air. Echoes may be heard surface from the source, given that\nmore than once due to successive or the speed of sound is 342 m s\u20131?\nmultiple reflections. The rolling of thunder\nis due to the successive reflections of the 11.3.3U SES OF MULTIPLE REFLECTION\nsound from a number of reflecting surfaces,\nOF SOUND\nsuch as the clouds and the land.\n1. Megaphones or loudhailers, horns,\n11.3.2R\nEVERBERATION musical instruments such as trumpets\nand shehanais, are all designed to send\nA sound created in a big hall will persist\nsound in a particular direction without\nby repeated reflection from the walls until\nspreading it in all directions, as shown\nit is reduced to a value where it is no longer\naudible. The repeated reflection that in Fig 11.10.\nresults in this persistence of sound is\ncalled reverberation. In an auditorium or\nbig hall excessive reverberation is highly\nundesirable. To reduce reverberation, the\nroof and walls of the auditorium are\ngenerally covered with sound-absorbent\nmaterials like compressed fibreboard, Megaphone\nrough plaster or draperies. The seat\nmaterials are also selected on the basis of\ntheir sound absorbing properties.\nHorn\nExample 11.2 A person clapped his hands\nnear a cliff and heard the echo after 2 s. Fig 11.10: A megaphone and a horn.\n134 SCIENCE\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
topic: persistent://default/default/f81812c1-3d1d-40de-83b4-4d1583367f4e
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{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 8, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "In these instruments, a tube followed\nby a conical opening reflects sound\nsuccessively to guide most of the\nsound waves from the source in the\nforward direction towards the\naudience.\n2. Stethoscope is a medical instrument\nused for listening to sounds produced\nwithin the body, mainly in the heart or\nlungs. In stethoscopes the sound of the\npatient\u2019s heartbeat reaches the doctor\u2019s\nears by multiple reflection of sound, as\nshown in Fig.11.11.\nFig. 11.13: Sound board used in a big hall.\nQ\nuestion\n1. Why are the ceilings of concert\nhalls curved?\n11.4 Range of Hearing\nFig.11.11: Stethoscope\nThe audible range of sound for human beings\n3. Generally the ceilings of concert halls,\nextends from about 20 Hz to 20000 Hz (one\nconference halls and cinema halls are\nHz = one cycle/s). Children under the age of\ncurved so that sound after reflection\nfive and some animals, such as dogs can hear\nreaches all corners of the hall, as\nup to 25 kHz (1 kHz = 1000 Hz). As people\nshown in Fig 11.12. Sometimes a\ngrow older their ears become less sensitive to\ncurved soundboard may be placed\nhigher frequencies. Sounds of frequencies\nbehind the stage so that the sound,\nbelow 20 Hz are called infrasonic sound or\nafter reflecting from the sound board,\ninfrasound. If we could hear infrasound we\nspreads evenly across the width of the\nwould hear the vibrations of a pendulum just\nhall (Fig 11.13).\nas we hear the vibrations of the wings of a bee.\nRhinoceroses communicate using infrasound\nof frequency as low as 5 Hz. Whales and\nelephants produce sound in the infrasound\nrange. It is observed that some animals get\ndisturbed before earthquakes. Earthquakes\nproduce low-frequency infrasound before the\nmain shock waves begin which possibly alert\nthe animals. Frequencies higher than 20 kHz\nare called ultrasonic sound or ultrasound.\nUltrasound is produced by animals such as\ndolphins, bats and porpoises. Moths of certain\nfamilies have very sensitive hearing equipment.\nFig. 11.12: Curved ceiling of a conference hall. These moths can hear the high frequency\nSOUND 135\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
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{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 9, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "squeaks of the bat and know when a bat in construction of big structures like\nis flying nearby, and are able to escape buildings, bridges, machines and also\ncapture. Rats also play games by scientific equipment. The cracks or\nproducing ultrasound. holes inside the metal blocks, which\nare invisible from outside reduces the\nstrength of the structure. Ultrasonic\nHearing Aid: People with hearing loss may waves are allowed to pass through the\nneed a hearing aid. A hearing aid is an metal block and detectors are used to\nelectronic, battery operated device. The\ndetect the transmitted waves. If there\nhearing aid receives sound through a\nis even a small defect, the ultrasound\nmicrophone. The microphone converts the\ngets reflected back indicating the\nsound waves to electrical signals. These\npresence of the flaw or defect, as shown\nelectrical signals are amplified by an\nin Fig. 11.14.\namplifier. The amplified electrical signals\nare given to a speaker of the hearing aid.\nThe speaker converts the amplified\nelectrical signal to sound and sends to the\near for clear hearing.\nQ\nuestions\n1. What is the audible range of the\naverage human ear?\n2. What is the range of frequencies\nFig 11.14: Ultrasound is reflected back from the\nassociated with defective locations inside a metal block.\n(a) Infrasound?\n(b) Ultrasound? Ordinary sound of longer wavelengths\ncannot be used for such purpose as it will\n11.5 Applications of Ultrasound bend around the corners of the defective\nlocation and enter the detector.\nUltrasounds are high frequency waves. \u2022 Ultrasonic waves are made to reflect\nUltrasounds are able to travel along well-\nfrom various parts of the heart and\ndefined paths even in the presence of\nform the image of the heart. This tech-\nobstacles. Ultrasounds are used extensively\nnique is called \u2018echocardiography\u2019.\nin industries and for medical purposes. \u2022 Ultrasound scanner is an instrument\n\u2022 Ultrasound is generally used to clean\nwhich uses ultrasonic waves for\nparts located in hard-to-reach places,\ngetting images of internal organs of the\nfor example, spiral tube, odd shaped\nhuman body. A doctor may image the\nparts, electronic components, etc.\npatient\u2019s organs, such as the liver, gall\nObjects to be cleaned are placed in a\nbladder, uterus, kidney, etc. It helps\ncleaning solution and ultrasonic waves\nthe doctor to detect abnormalities,\nare sent into the solution. Due to\nsuch as stones in the gall bladder and\nthe high frequency, the particles of\nkidney or tumours in different organs.\ndust, grease and dirt get detached and\nIn this technique the ultrasonic waves\ndrop out. The objects thus get\nthoroughly cleaned. travel through the tissues of the body\n\u2022 Ultrasounds can be used to detect and get reflected from a region where\ncracks and flaws in metal blocks. there is a change of tissue density.\n136 SCIENCE\nMetallic components are generally used\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
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{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 10, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "squeaks of the bat and know when a bat in construction of big structures like\nis flying nearby, and are able to escape buildings, bridges, machines and also\ncapture. Rats also play games by scientific equipment. The cracks or\nproducing ultrasound. holes inside the metal blocks, which\nare invisible from outside reduces the\nstrength of the structure. Ultrasonic\nHearing Aid: People with hearing loss may waves are allowed to pass through the\nneed a hearing aid. A hearing aid is an metal block and detectors are used to\nelectronic, battery operated device. The\ndetect the transmitted waves. If there\nhearing aid receives sound through a\nis even a small defect, the ultrasound\nmicrophone. The microphone converts the\ngets reflected back indicating the\nsound waves to electrical signals. These\npresence of the flaw or defect, as shown\nelectrical signals are amplified by an\nin Fig. 11.14.\namplifier. The amplified electrical signals\nare given to a speaker of the hearing aid.\nThe speaker converts the amplified\nelectrical signal to sound and sends to the\near for clear hearing.\nQ\nuestions\n1. What is the audible range of the\naverage human ear?\n2. What is the range of frequencies\nFig 11.14: Ultrasound is reflected back from the\nassociated with defective locations inside a metal block.\n(a) Infrasound?\n(b) Ultrasound? Ordinary sound of longer wavelengths\ncannot be used for such purpose as it will\n11.5 Applications of Ultrasound bend around the corners of the defective\nlocation and enter the detector.\nUltrasounds are high frequency waves. \u2022 Ultrasonic waves are made to reflect\nUltrasounds are able to travel along well-\nfrom various parts of the heart and\ndefined paths even in the presence of\nform the image of the heart. This tech-\nobstacles. Ultrasounds are used extensively\nnique is called \u2018echocardiography\u2019.\nin industries and for medical purposes. \u2022 Ultrasound scanner is an instrument\n\u2022 Ultrasound is generally used to clean\nwhich uses ultrasonic waves for\nparts located in hard-to-reach places,\ngetting images of internal organs of the\nfor example, spiral tube, odd shaped\nhuman body. A doctor may image the\nparts, electronic components, etc.\npatient\u2019s organs, such as the liver, gall\nObjects to be cleaned are placed in a\nbladder, uterus, kidney, etc. It helps\ncleaning solution and ultrasonic waves\nthe doctor to detect abnormalities,\nare sent into the solution. Due to\nsuch as stones in the gall bladder and\nthe high frequency, the particles of\nkidney or tumours in different organs.\ndust, grease and dirt get detached and\nIn this technique the ultrasonic waves\ndrop out. The objects thus get\nthoroughly cleaned. travel through the tissues of the body\n\u2022 Ultrasounds can be used to detect and get reflected from a region where\ncracks and flaws in metal blocks. there is a change of tissue density.\n136 SCIENCE\nMetallic components are generally used\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
topic: persistent://default/default/f81812c1-3d1d-40de-83b4-4d1583367f4e
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{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 11, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "These waves are then converted into examination of the foetus during\nelectrical signals that are used to pregnancy to detect congenial defects\ngenerate images of the organ. These and growth abnormalities.\nimages are then displayed on a monitor \u2022 Ultrasound may be employed to break\nor printed on a film. This technique small \u2018stones\u2019 formed in the kidneys\nis called \u2018ultrasonography\u2019. into fine grains. These grains later get\nUltrasonography is also used for flushed out with urine.\nWhat\nyou have\nlearnt\n\u2022 Sound is produced due to vibration of different objects.\n\u2022 Sound travels as a longitudinal wave through a material\nmedium.\n\u2022 Sound travels as successive compressions and rarefactions\nin the medium.\n\u2022 In sound propagation, it is the energy of the sound that\ntravels and not the particles of the medium.\n\u2022 The change in density from one maximum value to the\nminimum value and again to the maximum value makes\none complete oscillation.\n\u2022 The distance between two consecutive compressions or two\nconsecutive rarefactions is called the wavelength, \u03bb.\n\u2022 The time taken by the wave for one complete oscillation of\nthe density or pressure of the medium is called the time\nperiod, T.\n\u2022 The number of complete oscillations per unit time is called\n1\nv= .\nthe frequency (\u03bd),\nT\n\u2022 The speed v, frequency \u03bd, and wavelength \u03bb, of sound are\nrelated by the equation, v = \u03bb\u03bd.\n\u2022 The speed of sound depends primarily on the nature and\nthe temperature of the transmitting medium.\n\u2022 The law of reflection of sound states that the directions in\nwhich the sound is incident and reflected make equal angles\nwith the normal to the reflecting surface at the point of\nincidence and the three lie in the same plane.\n\u2022 For hearing a distinct sound, the time interval between the\noriginal sound and the reflected one must be at least 0.1 s.\n\u2022 The persistence of sound in an auditorium is the result of\nrepeated reflections of sound and is called reverberation.\nSOUND 137\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
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{"source": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "file_path": "/home/ash/Work_Assignments/sarvam-AI-Assignment/pdf_data/iesc111.pdf", "page": 12, "total_pages": 14, "Author": "admin", "CreationDate": "D:20220920145403+05'30'", "Creator": "Bullzip PDF Printer (12.2.0.2905)", "ModDate": "D:20230309122342+05'30'", "Producer": "PDF Printer / www.bullzip.com / FG / Freeware Edition (max 10 users)", "Title": "D:\\Textbooks\\Rationalised Books\\0964-Science\\1 Source Files\\Chapter-11\\CHAP 11.pmd", "chroma:document": "\u2022 Sound properties such as pitch, loudness and quality are\ndetermined by the corresponding wave properties.\n\u2022 Loudness is a physiological response of the ear to the intensity\nof sound.\n\u2022 The amount of sound energy passing each second through\nunit area is called the intensity of sound.\n\u2022 The audible range of hearing for average human beings is in\nthe frequency range of 20 Hz \u2013 20 kHz.\n\u2022 Sound waves with frequencies below the audible range are\ntermed \u201cinfrasonic\u201d and those above the audible range are\ntermed \u201cultrasonic\u201d.\n\u2022 Ultrasound has many medical and industrial applications.\nExercises\n1. What is sound and how is it produced?\n2. Describe with the help of a diagram, how compressions and\nrarefactions are produced in air near a source of sound.\n3. Why is sound wave called a longitudinal wave?\n4. Which characteristic of the sound helps you to identify your\nfriend by his voice while sitting with others in a dark room?\n5. Flash and thunder are produced simultaneously. But\nthunder is heard a few seconds after the flash is seen, why?\n6. A person has a hearing range from 20 Hz to 20 kHz. What\nare the typical wavelengths of sound waves in air\ncorresponding to these two frequencies? Take the speed of\nsound in air as 344 m s\u20131.\n7. Two children are at opposite ends of an aluminium rod. One\nstrikes the end of the rod with a stone. Find the ratio of\ntimes taken by the sound wave in air and in aluminium to\nreach the second child.\n8. The frequency of a source of sound is 100 Hz. How many\ntimes does it vibrate in a minute?\n9. Does sound follow the same laws of reflection as light does?\nExplain.\n10. When a sound is reflected from a distant object, an echo is\nproduced. Let the distance between the reflecting surface\nand the source of sound production remains the same. Do\nyou hear echo sound on a hotter day?\n11. Give two practical applications of reflection of sound waves.\n12. A stone is dropped from the top of a tower 500 m high into a\npond of water at the base of the tower. When is the splash\nheard at the top? Given, g = 10 m s\u20132 and speed of sound =\n340 m s\u20131.\n138 SCIENCE\nRationalised 2023-24\n"}


created_at: 2024-09-26 04:33:25
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11
C
hapter
SSSSS
OOOOOUUUUUNNNNNDDDDD
Everyday we hear sounds from various
sources like humans, birds, bells, machines,
vehicles, televisions, radios etc. Sound is a
form of energy which produces a sensation
of hearing in our ears. There are also other
forms of energy like mechanical energy, light
energy, etc. We have talked about mechanical
energy in the previous chapters. You have
been taught about conservation of energy,
which states that we can neither create nor
destroy energy. We can just change it from
one form to another. When you clap, a sound
is produced. Can you produce sound without
utilising your energy? Which form of energy
did you use to produce sound? In this
Fig. 11.1: Vibrating tuning fork just touching the
chapter we are going to learn how sound is
suspended table tennis ball.
produced and how it is transmitted through
a medium and received by our ears.
Activity _____________11.2
11.1 Production of Sound
• Fill water in a beaker or a glass up to
the brim. Gently touch the water surface
Activity _____________11.1 with one of the prongs of the vibrating
tuning fork, as shown in Fig. 11.2.
• Take a tuning fork and set it vibrating • Next dip the prongs of the vibrating
by striking its prong on a rubber pad. tuning fork in water, as shown in Fig.
Bring it near your ear. 11.3.
• Do you hear any sound? • Observe what happens in both the
• Touch one of the prongs of the vibrating cases.
tuning fork with your finger and share • Discuss with your friends why this
your experience with your friends. happens.
• Now, suspend a table tennis ball or a
small plastic ball by a thread from a
support [Take a big needle and a
thread, put a knot at one end of the
thread, and then with the help of the
needle pass the thread through the
ball]. Touch the ball gently with the
prong of a vibrating tuning
fork (Fig. 11.1).
• Observe what happens and discuss
with your friends. Fig. 11.2: One of the prongs of the vibrating tuning
fork touching the water surface.
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the vibrating object to the ear. A particle of
the medium in contact with the vibrating
object is first displaced from its equilibrium
position. It then exerts a force on the adjacent
particle. As a result of which the adjacent
particle gets displaced from its position of
rest. After displacing the adjacent particle the
first particle comes back to its original
position. This process continues in the
medium till the sound reaches your ear. The
disturbance created by a source of sound in
Fig. 11.3: Both the prongs of the vibrating tuning the medium travels through the medium and
fork dipped in water not the particles of the medium.
A wave is a disturbance that moves
From the above activities what do you through a medium when the particles of the
conclude? Can you produce sound without medium set neighbouring particles into
a vibrating object? motion. They in turn produce similar motion
In the above activities we have produced in others. The particles of the medium do not
sound by striking the tuning fork. We can move forward themselves, but the
also produce sound by plucking, scratching, disturbance is carried forward. This is what
rubbing, blowing or shaking different objects. happens during propagation of sound in a
As per the above activities what do we do to medium, hence sound can be visualised as a
the objects? We set the objects vibrating and wave. Sound waves are characterised by the
produce sound. Vibration means a kind of motion of particles in the medium and are
rapid to and fro motion of an object. The called mechanical waves.
sound of the human voice is produced due Air is the most common medium through
to vibrations in the vocal cords. When a bird which sound travels. When a vibrating object
moves forward, it pushes and compresses the
flaps its wings, do you hear any sound? Think
air in front of it creating a region of high
how the buzzing sound accompanying a bee
pressure. This region is called a compression
is produced. A stretched rubber band when
(C), as shown in Fig. 11.4. This compression
plucked vibrates and produces sound. If you
starts to move away from the vibrating object.
have never done this, then do it and observe
When the vibrating object moves backwards,
the vibration of the stretched rubber band.
it creates a region of low pressure called
Activity _____________11.3 rarefaction (R), as shown in Fig. 11.4. As the
object moves back and forth rapidly, a series
• Make a list of different types of of compressions and rarefactions is created in
musical instruments and discuss the air. These make the sound wave that
with your friends which part of the
instrument vibrates to produce
sound.
11.2 Propagation of Sound
Sound is produced by vibrating objects. The
matter or substance through which sound
is transmitted is called a medium. It can be
solid, liquid or gas. Sound moves through a
medium from the point of generation to the
listener. When an object vibrates, it sets the
Fig. 11.4: A vibrating object creating a series of
particles of the medium around it vibrating.
compressions (C) and rarefactions (R) in
The particles do not travel all the way from the medium.
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propagates through the medium. The regions where the coils become closer
Compression is the region of high pressure are called compressions (C) and the regions
and rarefaction is the region of low pressure. where the coils are further apart are called
Pressure is related to the number of particles
rarefactions (R). As we already know, sound
of a medium in a given volume. More density
propagates in the medium as a series of
of the particles in the medium gives more
compressions and rarefactions. Now, we can
pressure and vice versa. Thus, propagation
compare the propagation of disturbance in a
of sound can be visualised as propagation of
slinky with the sound propagation in the
density variations or pressure variations in
medium. These waves are called longitudinal
the medium.
Q waves. In these waves the individual particles
uestion of the medium move in a direction parallel to
the direction of propagation of the disturbance.
1. How does the sound produced by The particles do not move from one place to
a vibrating object in a medium another but they simply oscillate back and
reach your ear? forth about their position of rest. This is
2. Explain how sound is produced exactly how a sound wave propagates, hence
by your school bell. sound waves are longitudinal waves.
3. Why are sound waves called There is also another type of wave, called
mechanical waves? a transverse wave. In a transverse wave
4. Suppose you and your friend are particles do not oscillate along the direction
on the moon. Will you be able to of wave propagation but oscillate up and down
hear any sound produced by about their mean position as the wave travels.
your friend? Thus, a transverse wave is the one in which
the individual particles of the medium move
11.2.1S about their mean positions in a direction
OUND WAVES ARE LONGITUDINAL
perpendicular to the direction of wave
WAVES
propagation. When we drop a pebble in a
Activity _____________11.4 pond, the waves you see on the water surface
is an example of transverse wave. Light is a
• Take a slinky. Ask your friend to hold transverse wave but for light, the oscillations
one end. You hold the other end.
are not of the medium particles or their
Now stretch the slinky as shown in
pressure or density— it is not a mechanical
Fig. 11.5(a). Then give it a sharp push
wave. You will come to know more about
towards your friend.
transverse waves in higher classes.
• What do you notice? If you move your
hand pushing and pulling the slinky
11.2.2C
alternatively, what will you observe? HARACTERISTICS OF A SOUND
• If you mark a dot on the slinky, you
WAVE
will observe that the dot on the slinky
will move back and forth parallel to We can describe a sound wave by its
the direction of the propagation of the • frequency
disturbance.
• amplitude and
• speed.
A sound wave in graphic form is shown in
(a)
Fig. 11.6(c), which represents how density and
pressure change when the sound wave moves
in the medium. The density as well as the
pressure of the medium at a given time varies
(b) with distance, above and below the average
Fig. 11.5: Longitudinal wave in a slinky. value of density and pressure. Fig. 11.6(a) and
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Fig. 11.6(b) represent the density and
Heinrich Rudolph Hertz
pressure variations, respectively, as a sound
was born on 22 February
wave propagates in the medium.
1857 in Hamburg,
Compressions are the regions where
Germany and educated at
particles are crowded together and the University of Berlin. He
represented by the upper portion of the curve confirmed J.C. Maxwell’s
in Fig. 11.6(c). The peak represents the region electromagnetic theory by
of maximum compression. Thus, his experiments. He laid the
compressions are regions where density as H. R. Hertz foundation for future
well as pressure is high. Rarefactions are the development of radio, telephone, telegraph
regions of low pressure where particles are and even television. He also discovered the
spread apart and are represented by the photoelectric effect which was later
valley, that is, the lower portion of the curve explained by Albert Einstein. The SI unit of
frequency was named as hertz in his honour.
in Fig. 11.6(c). A peak is called the crest and a
valley is called the trough of a wave.
The distance between two consecutive Frequency tells us how frequently an
compressions (C) or two consecutive event occurs. Suppose you are beating a
rarefactions (R) is called the wavelength, as drum. How many times you are beating the
shown in Fig. 11.6(c), The wavelength is drum in unit time is called the frequency of
usually represented by λ (Greek letter your beating the drum. We know that when
lambda). Its SI unit is metre (m). sound is propagated through a medium, the
Fig. 11.6: Sound propagates as density or pressure variations as shown in (a) and (b), (c) represents
graphically the density and pressure variations.
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density of the medium oscillates between a
maximum value and a minimum value. The
change in density from the maximum value
to the minimum value, then again to the
maximum value, makes one complete
oscillation. The number of such oscillations
per unit time is the frequency of the sound
wave. If we can count the number of the
compressions or rarefactions that cross us
per unit time, we will get the frequency of
the sound wave. It is usually represented by
ν (Greek letter, nu). Its SI unit is hertz
(symbol, Hz).
The time taken by two consecutive
compressions or rarefactions to cross a fixed
point is called the time period of the wave. In
other words, we can say that the time taken
for one complete oscillation is called the time
period of the sound wave. It is represented by Fig. 11.7: Low pitch sound has low frequency and
high pitch of sound has high frequency.
the symbol T. Its SI unit is second (s).
Frequency and time period are related as as shown in Fig. 11.6(c). For sound its unit
follows:
will be that of density or pressure.
1
v = The loudness or softness of a sound is
T determined basically by its amplitude. The
amplitude of the sound wave depends upon
A violin and a flute may both be played at
the force with which an object is made to
the same time in an orchestra. Both sounds
vibrate. If we strike a table lightly, we hear a
travel through the same medium, that is, air
soft sound because we produce a sound wave
and arrive at our ear at the same time. Both
sounds travel at the same speed irrespective
of the source. But the sounds we receive are
different. This is due to the different
characteristics associated with the sound.
Pitch is one of the characteristics.
How the brain interprets the frequency
of an emitted sound is called its pitch. The
faster the vibration of the source, the
higher is the frequency and the higher is
the pitch, as shown in Fig. 11.7. Thus, a
high pitch sound corresponds to more
number of compressions and rarefactions
passing a fixed point per unit time.
Objects of different sizes and conditions
vibrate at different frequencies to produce
sounds of different pitch.
The magnitude of the maximum
disturbance in the medium on either side of
the mean value is called the amplitude of the
Fig. 11.8: Soft sound has small amplitude and
wave. It is usually represented by the letter A,
louder sound has large amplitude.
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of less energy (amplitude). If we hit the table
Example 11.1 A sound wave has a
hard we hear a louder sound. Can you tell
frequency of 2 kHz and wave length
why? A sound wave spreads out from its
35 cm. How long will it take to travel
source. As it moves away from the source its 1.5 km?
amplitude as well as its loudness decreases.
Solution:
Louder sound can travel a larger distance as
it is associated with higher energy. Fig. 11.8 Given,
shows the wave shapes of a loud and a soft Frequency, ν = 2 kHz = 2000 Hz
sound of the same frequency. Wavelength, λ = 35 cm = 0.35 m
The quality or timber of sound is that
We know that speed, v of the wave
characteristic which enables us to distinguish
= wavelength × frequency
one sound from another having the same pitch
v = λ ν
and loudness. The sound which is more
= 0.35 m 2000 Hz = 700 m/s
pleasant is said to be of a rich quality. A sound
The time taken by the wave to travel a
of single frequency is called a tone. The sound
distance, d of 1.5 km is
which is produced due to a mixture of several
frequencies is called a note and is pleasant to
listen to. Noise is unpleasant to the ear! Music
is pleasant to hear and is of rich quality. Thus sound will take 2.1 s to travel a
Q
distance of 1.5 km.
uestions Q
uestions
1. Which wave property determines
(a) loudness, (b) pitch?
1. What are wavelength, frequency,
2. Guess which sound has a higher
time period and amplitude of a
pitch: guitar or car horn?
sound wave?
2. How are the wavelength and
frequency of a sound wave
The speed of sound is defined as the
related to its speed?
distance which a point on a wave, such as a
3. Calculate the wavelength of a
compression or a rarefaction, travels per unit
sound wave whose frequency is
time.
220 Hz and speed is 440 m/s in
We know,
a given medium.
speed, v = distance / time
4. A person is listening to a tone of
l
500 Hz sitting at a distance of
=
T 450 m from the source of the
sound. What is the time interval
Here λ is the wavelength of the sound wave. It between successive compressions
is the distance travelled by the sound wave in from the source?
one time period (T) of the wave. Thus,
The amount of sound energy passing each
second through unit area is called the intensity
v = λ ν
of sound. We sometimes use the terms
“loudness” and “intensity” interchangeably,
or v = λ ν
but they are not the same. Loudness is a
That is, speed = wavelength × frequency.
measure of the response of the ear to the sound.
The speed of sound remains almost the
Even when two sounds are of equal intensity,
same for all frequencies in a given medium
we may hear one as louder than the other
under the same physical conditions.
simply because our ear detects it better.
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Q
Q
uestion
uestion
1. Distinguish between loudness
1. In which of the three media, air,
and intensity of sound.
water or iron, does sound travel
the fastest at a particular
11.2.3S
PEED OF SOUND IN DIFFERENT temperature?
MEDIA
Sound propagates through a medium at a finite 11.3 Reflection of Sound
speed. The sound of a thunder is heard a little
Sound bounces off a solid or a liquid like a
later than the flash of light is seen. So, we can
rubber ball bounces off a wall. Like light, sound
make out that sound travels with a speed
gets reflected at the surface of a solid or liquid
which is much less than the speed of light. The
and follows the same laws of reflection as you
speed of sound depends on the properties of
have studied in earlier classes. The directions
the medium through which it travels. You will
in which the sound is incident and is reflected
learn about this dependence in higher classes.
make equal angles with the normal to the
The speed of sound in a medium depends on
reflecting surface at the point of incidence, and
temperature of the medium. The speed of
the three are in the same plane. An obstacle of
sound decreases when we go from solid to
large size which may be polished or rough is
gaseous state. In any medium as we increase
needed for the reflection of sound waves.
the temperature, the speed of sound increases.
For example, the speed of sound in air is 331 Activity _____________11.5
m s–1 at 0 ºC and 344 m s–1 at 22 ºC. The speeds
of sound at a particular temperature in various • Take two identical pipes, as shown in
media are listed in Table 11.1. You need not Fig. 11.9. You can make the pipes
memorise the values. using chart paper. The length of the
pipes should be sufficiently long
as shown.
Table 11.1: Speed of sound in
• Arrange them on a table near a wall.
different media at 25 ºC
• Keep a clock near the open end of one
of the pipes and try to hear the sound
State Substance Speed in m/s of the clock through the other pipe.
• Adjust the position of the pipes so
Solids Aluminium 6420
that you can best hear the sound of
Nickel 6040 the clock.
Steel 5960 • Now, measure the angles of incidence
and reflection and see the
Iron 5950
relationship between the angles.
Brass 4700 • Lift the pipe on the right vertically
to a small height and observe
Glass (Flint) 3980
what happens.
Liquids Water (Sea) 1531 (In place of a clock, a mobile phone
on vibrating mode may also be used.)
Water (distilled) 1498
Ethanol 1207
Methanol 1103
Gases Hydrogen 1284
Helium 965
Air 346
Oxygen 316
Sulphur dioxide 213
Fig. 11.9: Reflection of sound
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11.3.1E CHO What is the distance of the cliff from the
person if the speed of the sound, v is
If we shout or clap near a suitable reflecting
taken as 346 m s–1?
object such as a tall building or a
mountain,we will hear the same sound
Solution:
again a little later. This sound which we
hear is called an echo. The sensation of Given,
sound persists in our brain for about 0.1 Speed of sound, v = 346 m s–1
s. To hear a distinct echo the time interval Time taken for hearing the echo,
between the original sound and the t = 2 s
reflected one must be at least 0.1s. If we Distance travelled by the sound
take the speed of sound to be 344 m/s at a
= v × t = 346 m s–1 × 2 s = 692 m
given temperature, say at 22 ºC in air, the
In 2 s sound has to travel twice the
sound must go to the obstacle and reach
distance between the cliff and the
back the ear of the listener on reflection after
person. Hence, the distance between the
0.1s. Hence, the total distance covered by
cliff and the person
the sound from the point of generation to
= 692 m/2 = 346 m.
the reflecting surface and back should be
at least (344 m/s) × 0.1 s = 34.4 m. Thus, Q
uestion
for hearing distinct echoes, the minimum
distance of the obstacle from the source of
1. An echo is heard in 3 s. What is
sound must be half of this distance, that
the distance of the reflecting
is, 17.2 m. This distance will change with
the temperature of air. Echoes may be heard surface from the source, given that
more than once due to successive or the speed of sound is 342 m s–1?
multiple reflections. The rolling of thunder
is due to the successive reflections of the 11.3.3U SES OF MULTIPLE REFLECTION
sound from a number of reflecting surfaces,
OF SOUND
such as the clouds and the land.
1. Megaphones or loudhailers, horns,
11.3.2R
EVERBERATION musical instruments such as trumpets
and shehanais, are all designed to send
A sound created in a big hall will persist
sound in a particular direction without
by repeated reflection from the walls until
spreading it in all directions, as shown
it is reduced to a value where it is no longer
audible. The repeated reflection that in Fig 11.10.
results in this persistence of sound is
called reverberation. In an auditorium or
big hall excessive reverberation is highly
undesirable. To reduce reverberation, the
roof and walls of the auditorium are
generally covered with sound-absorbent
materials like compressed fibreboard, Megaphone
rough plaster or draperies. The seat
materials are also selected on the basis of
their sound absorbing properties.
Horn
Example 11.2 A person clapped his hands
near a cliff and heard the echo after 2 s. Fig 11.10: A megaphone and a horn.
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In these instruments, a tube followed
by a conical opening reflects sound
successively to guide most of the
sound waves from the source in the
forward direction towards the
audience.
2. Stethoscope is a medical instrument
used for listening to sounds produced
within the body, mainly in the heart or
lungs. In stethoscopes the sound of the
patient’s heartbeat reaches the doctor’s
ears by multiple reflection of sound, as
shown in Fig.11.11.
Fig. 11.13: Sound board used in a big hall.
Q
uestion
1. Why are the ceilings of concert
halls curved?
11.4 Range of Hearing
Fig.11.11: Stethoscope
The audible range of sound for human beings
3. Generally the ceilings of concert halls,
extends from about 20 Hz to 20000 Hz (one
conference halls and cinema halls are
Hz = one cycle/s). Children under the age of
curved so that sound after reflection
five and some animals, such as dogs can hear
reaches all corners of the hall, as
up to 25 kHz (1 kHz = 1000 Hz). As people
shown in Fig 11.12. Sometimes a
grow older their ears become less sensitive to
curved soundboard may be placed
higher frequencies. Sounds of frequencies
behind the stage so that the sound,
below 20 Hz are called infrasonic sound or
after reflecting from the sound board,
infrasound. If we could hear infrasound we
spreads evenly across the width of the
would hear the vibrations of a pendulum just
hall (Fig 11.13).
as we hear the vibrations of the wings of a bee.
Rhinoceroses communicate using infrasound
of frequency as low as 5 Hz. Whales and
elephants produce sound in the infrasound
range. It is observed that some animals get
disturbed before earthquakes. Earthquakes
produce low-frequency infrasound before the
main shock waves begin which possibly alert
the animals. Frequencies higher than 20 kHz
are called ultrasonic sound or ultrasound.
Ultrasound is produced by animals such as
dolphins, bats and porpoises. Moths of certain
families have very sensitive hearing equipment.
Fig. 11.12: Curved ceiling of a conference hall. These moths can hear the high frequency
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squeaks of the bat and know when a bat in construction of big structures like
is flying nearby, and are able to escape buildings, bridges, machines and also
capture. Rats also play games by scientific equipment. The cracks or
producing ultrasound. holes inside the metal blocks, which
are invisible from outside reduces the
strength of the structure. Ultrasonic
Hearing Aid: People with hearing loss may waves are allowed to pass through the
need a hearing aid. A hearing aid is an metal block and detectors are used to
electronic, battery operated device. The
detect the transmitted waves. If there
hearing aid receives sound through a
is even a small defect, the ultrasound
microphone. The microphone converts the
gets reflected back indicating the
sound waves to electrical signals. These
presence of the flaw or defect, as shown
electrical signals are amplified by an
in Fig. 11.14.
amplifier. The amplified electrical signals
are given to a speaker of the hearing aid.
The speaker converts the amplified
electrical signal to sound and sends to the
ear for clear hearing.
Q
uestions
1. What is the audible range of the
average human ear?
2. What is the range of frequencies
Fig 11.14: Ultrasound is reflected back from the
associated with defective locations inside a metal block.
(a) Infrasound?
(b) Ultrasound? Ordinary sound of longer wavelengths
cannot be used for such purpose as it will
11.5 Applications of Ultrasound bend around the corners of the defective
location and enter the detector.
Ultrasounds are high frequency waves. • Ultrasonic waves are made to reflect
Ultrasounds are able to travel along well-
from various parts of the heart and
defined paths even in the presence of
form the image of the heart. This tech-
obstacles. Ultrasounds are used extensively
nique is called ‘echocardiography’.
in industries and for medical purposes. • Ultrasound scanner is an instrument
• Ultrasound is generally used to clean
which uses ultrasonic waves for
parts located in hard-to-reach places,
getting images of internal organs of the
for example, spiral tube, odd shaped
human body. A doctor may image the
parts, electronic components, etc.
patient’s organs, such as the liver, gall
Objects to be cleaned are placed in a
bladder, uterus, kidney, etc. It helps
cleaning solution and ultrasonic waves
the doctor to detect abnormalities,
are sent into the solution. Due to
such as stones in the gall bladder and
the high frequency, the particles of
kidney or tumours in different organs.
dust, grease and dirt get detached and
In this technique the ultrasonic waves
drop out. The objects thus get
thoroughly cleaned. travel through the tissues of the body
• Ultrasounds can be used to detect and get reflected from a region where
cracks and flaws in metal blocks. there is a change of tissue density.
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These waves are then converted into examination of the foetus during
electrical signals that are used to pregnancy to detect congenial defects
generate images of the organ. These and growth abnormalities.
images are then displayed on a monitor • Ultrasound may be employed to break
or printed on a film. This technique small ‘stones’ formed in the kidneys
is called ‘ultrasonography’. into fine grains. These grains later get
Ultrasonography is also used for flushed out with urine.
What
you have
learnt
• Sound is produced due to vibration of different objects.
• Sound travels as a longitudinal wave through a material
medium.
• Sound travels as successive compressions and rarefactions
in the medium.
• In sound propagation, it is the energy of the sound that
travels and not the particles of the medium.
• The change in density from one maximum value to the
minimum value and again to the maximum value makes
one complete oscillation.
• The distance between two consecutive compressions or two
consecutive rarefactions is called the wavelength, λ.
• The time taken by the wave for one complete oscillation of
the density or pressure of the medium is called the time
period, T.
• The number of complete oscillations per unit time is called
1
v= .
the frequency (ν),
T
• The speed v, frequency ν, and wavelength λ, of sound are
related by the equation, v = λν.
• The speed of sound depends primarily on the nature and
the temperature of the transmitting medium.
• The law of reflection of sound states that the directions in
which the sound is incident and reflected make equal angles
with the normal to the reflecting surface at the point of
incidence and the three lie in the same plane.
• For hearing a distinct sound, the time interval between the
original sound and the reflected one must be at least 0.1 s.
• The persistence of sound in an auditorium is the result of
repeated reflections of sound and is called reverberation.
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• Sound properties such as pitch, loudness and quality are
determined by the corresponding wave properties.
• Loudness is a physiological response of the ear to the intensity
of sound.
• The amount of sound energy passing each second through
unit area is called the intensity of sound.
• The audible range of hearing for average human beings is in
the frequency range of 20 Hz – 20 kHz.
• Sound waves with frequencies below the audible range are
termed “infrasonic” and those above the audible range are
termed “ultrasonic”.
• Ultrasound has many medical and industrial applications.
Exercises
1. What is sound and how is it produced?
2. Describe with the help of a diagram, how compressions and
rarefactions are produced in air near a source of sound.
3. Why is sound wave called a longitudinal wave?
4. Which characteristic of the sound helps you to identify your
friend by his voice while sitting with others in a dark room?
5. Flash and thunder are produced simultaneously. But
thunder is heard a few seconds after the flash is seen, why?
6. A person has a hearing range from 20 Hz to 20 kHz. What
are the typical wavelengths of sound waves in air
corresponding to these two frequencies? Take the speed of
sound in air as 344 m s–1.
7. Two children are at opposite ends of an aluminium rod. One
strikes the end of the rod with a stone. Find the ratio of
times taken by the sound wave in air and in aluminium to
reach the second child.
8. The frequency of a source of sound is 100 Hz. How many
times does it vibrate in a minute?
9. Does sound follow the same laws of reflection as light does?
Explain.
10. When a sound is reflected from a distant object, an echo is
produced. Let the distance between the reflecting surface
and the source of sound production remains the same. Do
you hear echo sound on a hotter day?
11. Give two practical applications of reflection of sound waves.
12. A stone is dropped from the top of a tower 500 m high into a
pond of water at the base of the tower. When is the splash
heard at the top? Given, g = 10 m s–2 and speed of sound =
340 m s–1.
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13. A sound wave travels at a speed of 339 m s–1. If its wavelength
is 1.5 cm, what is the frequency of the wave? Will it be
audible?
14. What is reverberation? How can it be reduced?
15. What is loudness of sound? What factors does it depend on?
16. How is ultrasound used for cleaning?
17. Explain how defects in a metal block can be detected using
ultrasound.
SOUND 139
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