Answer:
Wavefronts are the surfaces over which the vibrations due to sound wave have same value. For near sound source, wavefronts are considered spherical while for the distance source of sound the wavefronts are considered planar.
Sound
Q 1.
How is sound propagated through a material medium ? What is wave motion ?
Q 2.
By how much does the speed of sound increase with rise of temperature ?
Q 3.
A hospital uses an ultrasonic scanner to locate tumors in a tissue. What is the wavelength of sound in a tissue is which the speed of sound is 1.7 km/s. The operating frequency of the scanner is 4.2 MHz. (1MHz = 10
6 Hz).
Q 4.
What is a wave number?
Q 5.
What is audible range ?
Q 6.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 7.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 8.
How are compressions and rarefactions produced near a source of sound ?
Q 9.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 10.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 11.
What is infrasonic? Give an example.
Q 12.
What is Sound? Why it is important for us?
Q 13.
What are the factors speed of sound wave depends upon?
Q 14.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 15.
Fill in the blanks :
v = ? × ?
Q 16.
What is speed of sound in air?
Q 17.
What are ultrasonics?
Q 18.
Explain the working and application of a sonar.
Q 19.
What propagates along with the waves ?
Q 20.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is
440 m/s in a given medium.
Q 21.
Why are sound waves called mechanical waves ?
Q 23.
Why sound waves are called mechanical waves?
Q 24.
Three persons, A, B and C are made to hear a sound travelling through different mediums as given below:
| Persons | Medium |
| A | Iron Rod |
| B | Air |
| C | Water |
Who will hear the sound first? Why?
Q 25.
If 20 waves are produced per second, what is the frequency in hertz?
Q 26.
An observer standing at the sea coast observes 54 waves reaching the coast per minute.If the wavelength of a wave is 10 m,find the wave velocity.
Q 27.
Fill in the blanks :
In a __________ wave the particles of the medium oscillate in a direction perpendicular to the direction in which the wave propagates.
Q 28.
A sound wave travels at a speed of 339 ms
–1. If its wavelength is 1.5 cm, what is the frequency of the wave?
Q 29.
A person standing between two vertical cliffs and 680 m away from the nearest cliff,shouted.He heard the first echo after 4 s and the second echo 3 s later.Calculate (a) the speed of sound in air and (b) distance between the two cliffs.
Q 30.
An engine is approaching a hill at constant speed.When it is at a distance of 0.9 km,it blows a whisde,whose echo is heard by the driver after 5 s.If the speed of sound is 340 m/s,calculate the speed of the engine.
Q 31.
Explain how sound is produced by your school bell ?
Q 32.
How can you show that sound waves are longitudinal waves ?
Q 33.
Fill in the blanks :
The principle on which stethoscope works is _____ (reflection/ multiple reflection)
Q 34.
Fill in the blanks :
Sound travels as successive ____________ and _____________ in the medium.
Q 35.
Fill in the blanks :
Ripples waves on water surface are example of ____________.
Q 36.
Fill in the blanks :
If the time interval between original sound and reflected sound is more than 1/10 second then original sound and reflected sound can be heard clearly. This reflected sound is known as _______.
Q 37.
Fill in the blanks :
Loudness of sound is measured in ___________.
Q 38.
What is a mechanical wave?
Q 39.
Why transverse wave does not travel through air or gases?
Q 40.
Give an application use of ultrasonics.
Q 41.
Which wave characteristics determine the
(a) Loudness (b) pitch of sound?
Draw two different waveforms and mark these characteristics on it.
Q 42.
A person is listening to a tone of 500 Hz sitting at a distance of 450 m from the source of the sound. What is the time interval between successive compressions from the source?
Q 43.
A boat anchor is rocked by waves whose consecutive crests are 100 m apart.If the wave speed of the moving crests is 20 m/s,calculate the frequency at which the boat rocks.
Q 44.
The sonic boom of an aircraft has a time period of 0 00005 s.Calculate the frequency of the sound produced.
Q 45.
A wave of wavelength 0-60 cm is produced in air and it travels at a speed of 300 m/s.Will it be audible ?
Q 46.
A child hears an echo from a cliff 4 s after the sound of a pwerful cracker is produced.How far away is the cliff from the child ? (Take speed of sound in air as 340 m/s)
Q 47.
A man standing at 51 m from a wall fires a gun.Calculate the time after which an echo is heard.The speed of sound is 340 m/s.
Q 48.
A ship sends out ultrasound that returns from the seabed and is detected after 3.42 s.If the speed of the ultrasound through sea water is 1531 m/s,what is the distance of the seabed from the ship ?
Q 49.
sonar emits pulses on the surface of water which are detected after reflection from its bottom at a depth 1531 m.If the time interval between the emission and detection of the pulse is 2 s,find the speed of : sound in water.
Q 50.
Distinguish between loudness and intensity of sound.
