Question:
What is sound ? Discuss the method of its production.
Answer:
Refer to Art.6.2,Page 323; Art.6.3,Page 324.
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 are ultrasonics?
Q 17.
What propagates along with the waves ?
Q 18.
What is speed of sound in air?
Q 19.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is
440 m/s in a given medium.
Q 20.
Why are sound waves called mechanical waves ?
Q 21.
Explain the working and application of a sonar.
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.
Fill in the blanks :
Ripples waves on water surface are example of ____________.
Q 33.
Fill in the blanks :
Loudness of sound is measured in ___________.
Q 34.
What is a mechanical wave?
Q 35.
Why transverse wave does not travel through air or gases?
Q 36.
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 37.
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 38.
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 39.
Distinguish between loudness and intensity of sound.
Q 40.
What is loudness of sound ? What factors does it depend on ?
Q 41.
Which of the above two graphs : (a) and (b),[ Fig. representing the human voice is likely to be the male voice ? Give reson for your answer.
Q 42.
What are ultrasonics ?
Q 43.
Can you produce sound without utilizing energy ?
Q 44.
The sound of distant horses can be heard by applying the ear to the ground whereas it is inaudible if the ear is held a little distance above the ground.Explain.
Q 45.
How can you show that sound waves are longitudinal waves ?
Q 46.
What are transverse waves ?
Q 47.
Distinguish between music and noise.
Q 48.
What is SONAR ? How is it used to detect an underwater object and measure its distance
Q 49.
We see flash earlier than the thunder.Discuss.
Q 50.
Hearing may be damaged by excessive noise.So our ears sometimes need protection from continuous loud sound. Hearing damage depends on the sound intensity level (decibel level)and the exposure time,and the exact combinations vary for different people.Normally,at 90 dB,it takes 8 hours or less for the damage to receptor nerves to occur.Further,it is found that if the sound level is increased by 5 dB,the safe exposure limit is cut to half.
(a) How long will it take for a sound of a very loud lawn mower (or a motorcycle) of 95dB to damage the hearing ?
(b) What is the nonstop exposure time for a 105 dB sound to damage the ear ?
(c) What should be done to protect the society from the danger of losing the divine gift of hearing power ?
