Question:
Deaf people can be made to dance to music.Explain how ?
Answer:
If there is nothing wrong with the internal ear,deaf people can listen to music.This can be made possible by placing one end of a rod on a piano (or any other musical instrument) in such a way that it does not obstruct playing upon it.The other end of the rod can be gripped in the teeth.The music would reach the auditory nerve via rod and bones of the head.
Sound
Q 1.
What are the factors speed of sound wave depends upon?
Q 2.
What are ultrasonics?
Q 3.
What is a wave number?
Q 4.
How are compressions and rarefactions produced near a source of sound ?
Q 5.
What type of waves can travel in vacuum? Give example(s).
Q 6.
What is audible range ?
Q 7.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 8.
Explain how sound is produced by your school bell ?
Q 10.
How is sound propagated through a material medium ? What is wave motion ?
Q 11.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 12.
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 13.
Fill in the blanks :
Waves transport _________ not matter.
Q 14.
Fill in the blanks :
v = ? × ?
Q 15.
What is speed of sound in air?
Q 16.
How are the wavelength and frequency of a sound wave related to its speed?
Q 17.
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 18.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is
440 m/s in a given medium.
Q 19.
What is infrasonic? Give an example.
Q 20.
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 21.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 22.
What is the audible range of the average human ear ?
Q 23.
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
and speed of sound = 340 m/s.
Q 24.
What propagates along with the waves ?
Q 25.
Why do we use upholstered seats in theatres and halls ?
Q 26.
How can you show that sound waves are longitudinal waves ?
Q 27.
Sounds we hear inform us of the state of world around us,especially of that part of it which our other senses,such as touch and sight,cannot reach.Illustrate this with appropriate examples.
Q 28.
Fill in the blanks :
Number of oscillations completed by the oscillator in one second is known as ___________.
Q 29.
Fill in the blanks :
In a _____________ wave the particles of the medium oscillate in the direction in which the wave travels.
Q 30.
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 31.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 32.
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 33.
If 20 waves are produced per second, what is the frequency in hertz?
Q 34.
Give an application use of ultrasonics.
Q 35.
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 36.
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 37.
Give examples of longitudinal waves.
Q 38.
Can sound wave travel in vacuum?
Q 39.
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 40.
What type of wave is represented by density- distance graph?
Q 41.
What are wavelength,frequency,time period and amplitude of a sound wave ?
Q 42.
Write the name of the wave which propagates in terms of compressions and rarefactions.
Q 43.
Fill in the blanks :
If a body repeats its back and forth, to and fro or up and down motion along a certain path, about a fixed point, in a certain time interval then the motion of such objects is said to be _____________.
Q 44.
What is a mechanical wave?
Q 45.
What is reverberation?
Q 46.
Which wave characteristics determine the
(a) Loudness (b) pitch of sound?
Draw two different waveforms and mark these characteristics on it.
Q 47.
Guess which sound has a higher pitch: guitar or car horn?
Q 48.
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 49.
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 50.
Explain the working and application of a sonar.
