Question:
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 _______.
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.
How is sound propagated through a material medium ? What is wave motion ?
Q 3.
By how much does the speed of sound increase with rise of temperature ?
Q 4.
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 5.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 6.
How are compressions and rarefactions produced near a source of sound ?
Q 7.
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 8.
Fill in the blanks :
Number of oscillations completed by the oscillator in one second is known as ___________.
Q 9.
Fill in the blanks :
Ripples waves on water surface are example of ____________.
Q 10.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 11.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is
440 m/s in a given medium.
Q 12.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 13.
Fill in the blanks :
v = ? × ?
Q 14.
What is a mechanical wave?
Q 15.
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 16.
Why are sound waves called mechanical waves ?
Q 17.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 18.
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 19.
What is Sound? Why it is important for us?
Q 20.
What is speed of sound in air?
Q 21.
If 20 waves are produced per second, what is the frequency in hertz?
Q 22.
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 23.
A man fires a gun towards a hill and hears its echo after 5 s.He then moves 340 m towards the hill and fires his gun again.This time he hears the echo after 3 s.Calculate the speed of sound.
Q 24.
What is audible range ?
Q 25.
Distinguish between music and noise.
Q 26.
What is a longitudinal wave?
Q 27.
What is a wave number?
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.
What type of wave is represented by density- distance graph?
Q 30.
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 31.
What is the audible range of the average human ear ?
Q 33.
What is the difference between an echo and a reverberation ?
Q 34.
How can you show that sound waves are longitudinal waves ?
Q 35.
We see flash earlier than the thunder.Discuss.
Q 36.
Fill in the blanks :
If a body repeats its motion, within fix interval of time, along a certain path, about a fixed point, it is said to have ____________.
Q 37.
Fill in the blanks :
Waves transport _________ not matter.
Q 38.
Fill in the blanks :
Full form of SONAR is __________________________.
Q 39.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 40.
Fill in the blanks :
Sound having frequency more than 20,000Hz is known as ___________.
Q 41.
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 42.
Give examples of longitudinal waves.
Q 43.
What are wavefronts?
Q 44.
Suppose you and your friend are on the Moon. Will you be able to hear any sound produced by your friend?
Q 45.
Write differences between Transverse waves and Longitudinal waves.
Q 46.
What is reverberation?
Q 47.
Demonstrate an activity to show that sound requires a medium to travel.
Q 48.
Guess which sound has a higher pitch: guitar or car horn?
Q 49.
A boat anchor is rocked by waves whose consecutive crests are 100 m apart.If the wave speed of the moving crests is 20 m/s,calculate the frequency at which the boat rocks.
Q 50.
Calculate the wavelength of a sound wave having a frequency 300 Hz and speed 330 m/s.
