Question:
How can you make a building sound proof ?
Answer:
A building can be made sound proof by insulating it from its surroundings.The doors used in such buildings should be heavy and sound proof.All the surfaces including the floor,are also covered with several centimetres of highly absorbent materials such as rock wood or asbestos fibre.Further,absorbent deflectors are placed at suitable places in the building.
Sound
Q 1.
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 2.
Explain the working and application of a sonar.
Q 4.
What is reverberation?
Q 5.
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 6.
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 7.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 8.
How can you show that sound waves are longitudinal waves ?
Q 9.
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 10.
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 11.
How are compressions and rarefactions produced near a source of sound ?
Q 12.
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 13.
A longitudinal wave is produced on a slinky.The frequency of the wave is 25 Hz and it travels at a speed of 20 cm/s. Find the separation between consecutive positions of maximum compressions.
Q 14.
How is sound propagated through a material medium ? What is wave motion ?
Q 15.
What is a longitudinal wave?
Q 16.
Why do we use upholstered seats in theatres and halls ?
Q 17.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 18.
What is infrasonic? Give an example.
Q 19.
Demonstrate an activity to show that sound requires a medium to travel.
Q 20.
The sonic boom of an aircraft has a time period of 0 00005 s.Calculate the frequency of the sound produced.
Q 21.
Why are sound waves called mechanical waves ?
Q 22.
Distinguish between loudness and intensity of sound.
Q 23.
How is ultrasound used for cleaning ?
Q 24.
What propagates along with the waves ?
Q 25.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 26.
Can sound wave travel in vacuum?
Q 27.
What type of waves can travel in vacuum? Give example(s).
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.
Write differences between Transverse waves and Longitudinal waves.
Q 30.
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 31.
Describe with the help of a diagram,how compressions and rarefactions are produced in air near a source of sound.
Q 32.
What is audible range ?
Q 33.
What is acoustical transite ?
Q 34.
What is sound ? Discuss the method of its production.
Q 35.
On what factors does the speed of sound in a material depend ?
Q 36.
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
Q 37.
Fill in the blanks :
When we hear music, the medium through which the sound transmitted is __________ (solid, liquid, gas)
Q 38.
Fill in the blanks :
Number of oscillations completed by the oscillator in one second is known as ___________.
Q 39.
Fill in the blanks :
Waves which require a material medium for propagation are called _____________ waves. Example of such waves is _________. Light waves are ___________, because they can travel in vacuum.
Q 40.
Fill in the blanks :
Sound travels as successive ____________ and _____________ in the medium.
Q 41.
Fill in the blanks :
Waves transport _________ not matter.
Q 42.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 43.
Fill in the blanks :
Full form of SONAR is __________________________.
Q 44.
Fill in the blanks :
Sound having frequency less than 20Hz is known as ___________.
Q 45.
Fill in the blanks :
The distance between two consecutive compressions or two consecutive rarefactions is called the ______________.
Q 46.
What is a mechanical wave?
Q 47.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 48.
Why sound waves are called mechanical waves?
Q 49.
What is speed of sound in air?
Q 50.
Among solids, liquids and gases sound travels faster in which medium?
