Question:
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
Answer:
(i) You would not be able to enjoy music or speech,.
(ii) Only with great difficulty and long training would you learn to speak coherently.
(iii) It would be dangerous to move out in street because you could not hear an approaching car nor the warning of a bystander.
(iv) In short, half of life would not exist and the other half would be very complicated and dangerous.We should be thus grateful to God for giving us the faculty of hearing.
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.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 6.
What is audible range ?
Q 7.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
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 is speed of sound in air?
Q 14.
What are the factors speed of sound wave depends upon?
Q 15.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 16.
Fill in the blanks :
v = ? × ?
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.
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 26.
If 20 waves are produced per second, what is the frequency in hertz?
Q 27.
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 28.
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 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.
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 32.
Explain how sound is produced by your school bell ?
Q 33.
Distinguish between loudness and intensity of sound.
Q 34.
What is the audible range of the average human ear ?
Q 35.
How can you show that sound waves are longitudinal waves ?
Q 36.
What are transverse waves ?
Q 37.
Fill in the blanks :
The principle on which stethoscope works is _____ (reflection/ multiple reflection)
Q 38.
Fill in the blanks :
Sound travels as successive ____________ and _____________ in the medium.
Q 39.
Fill in the blanks :
Waves transport _________ not matter.
Q 40.
Fill in the blanks :
Ripples waves on water surface are example of ____________.
Q 41.
Fill in the blanks :
The distance between two consecutive compressions or two consecutive rarefactions is called the ______________.
Q 42.
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 43.
Fill in the blanks :
Loudness of sound is measured in ___________.
Q 44.
What is a mechanical wave?
Q 45.
What are wavefronts?
Q 46.
What type of waves can travel in vacuum? Give example(s).
Q 47.
Why transverse wave does not travel through air or gases?
Q 48.
Give an application use of ultrasonics.
Q 49.
Which wave characteristics determine the
(a) Loudness (b) pitch of sound?
Draw two different waveforms and mark these characteristics on it.
Q 50.
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?
