Question:
Distinguish between music and noise.
Answer:
Refer to Art. 6.19,Page 345.
Sound
Q 1.
How is sound propagated through a material medium ? What is wave motion ?
Q 2.
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 3.
By how much does the speed of sound increase with rise of temperature ?
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.
How are compressions and rarefactions produced near a source of sound ?
Q 8.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
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 are the factors speed of sound wave depends upon?
Q 13.
What is Sound? Why it is important for us?
Q 14.
What is speed of sound in air?
Q 15.
Explain the working and application of a sonar.
Q 16.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 17.
Fill in the blanks :
v = ? × ?
Q 18.
What are ultrasonics?
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.
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 29.
How can you show that sound waves are longitudinal waves ?
Q 30.
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 31.
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 32.
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 33.
Explain how sound is produced by your school bell ?
Q 34.
Distinguish between loudness and intensity of sound.
Q 35.
What is the audible range of the average human ear ?
Q 36.
What is loudness of sound ? What factors does it depend on ?
Q 37.
What are ultrasonics ?
Q 38.
Can you produce sound without utilizing energy ?
Q 39.
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 40.
What are transverse waves ?
Q 41.
What is SONAR ? How is it used to detect an underwater object and measure its distance
Q 42.
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 ?
Q 43.
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
Q 44.
Fill in the blanks :
The principle on which stethoscope works is _____ (reflection/ multiple reflection)
Q 45.
Fill in the blanks :
Sound travels as successive ____________ and _____________ in the medium.
Q 46.
Fill in the blanks :
Waves transport _________ not matter.
Q 47.
Fill in the blanks :
Ripples waves on water surface are example of ____________.
Q 48.
Fill in the blanks :
The distance between two consecutive compressions or two consecutive rarefactions is called the ______________.
Q 49.
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 50.
Fill in the blanks :
Loudness of sound is measured in ___________.
