Question:
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Answer:
longitudinal waves
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 3.
What is reverberation?
Q 4.
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 5.
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.
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 8.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 9.
How are compressions and rarefactions produced near a source of sound ?
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.
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 12.
How is sound propagated through a material medium ? What is wave motion ?
Q 13.
How can you show that sound waves are longitudinal waves ?
Q 14.
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 15.
What is a longitudinal wave?
Q 16.
Why do we use upholstered seats in theatres and halls ?
Q 17.
What is infrasonic? Give an example.
Q 18.
The sonic boom of an aircraft has a time period of 0 00005 s.Calculate the frequency of the sound produced.
Q 19.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 20.
What type of waves can travel in vacuum? Give example(s).
Q 21.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 22.
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 23.
Write differences between Transverse waves and Longitudinal waves.
Q 24.
Demonstrate an activity to show that sound requires a medium to travel.
Q 25.
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 26.
Why are sound waves called mechanical waves ?
Q 27.
Distinguish between loudness and intensity of sound.
Q 28.
How is ultrasound used for cleaning ?
Q 29.
What propagates along with the waves ?
Q 30.
What is acoustical transite ?
Q 31.
Fill in the blanks :
Sound travels as successive ____________ and _____________ in the medium.
Q 32.
Fill in the blanks :
Waves transport _________ not matter.
Q 33.
Fill in the blanks :
Full form of SONAR is __________________________.
Q 34.
Fill in the blanks :
Sound having frequency less than 20Hz is known as ___________.
Q 35.
What is a mechanical wave?
Q 36.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 37.
Why sound waves are called mechanical waves?
Q 38.
Can sound wave travel in vacuum?
Q 39.
What is speed of sound in air?
Q 40.
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 41.
What is a wave number?
Q 42.
How are the wavelength and frequency of a sound wave related to its speed?
Q 43.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is
440 m/s in a given medium.
Q 44.
If 20 waves are produced per second, what is the frequency in hertz?
Q 46.
Give an application use of ultrasonics.
Q 47.
What type of wave is represented by density- distance graph?
Q 48.
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 49.
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 50.
A bat emits ultrasonic sound of frequency 100 kHz in air.If this sound meets a water surface,what is the wavelength of (a) the reflected sound wave (b) the transmitted sound wave ?
Given speed of sound in air = 340 m/s and in water = 1486 m/s.
