Answer:
Wavefronts are the surfaces over which the vibrations due to sound wave have same value. For near sound source, wavefronts are considered spherical while for the distance source of sound the wavefronts are considered planar.
Sound
Q 1.
What are the factors speed of sound wave depends upon?
Q 2.
Fill in the blanks :
v = ? × ?
Q 3.
Explain how sound is produced by your school bell ?
Q 4.
What propagates along with the waves ?
Q 5.
Why do we use upholstered seats in theatres and halls ?
Q 6.
Explain how the human ear works.
Q 7.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 8.
Radio Ceylon broadcasts at 25 m.What is the frequency of the station ?
Q 9.
Fill in the blanks :
Loudness of sound is measured in ___________.
Q 10.
What is the audible range?
Q 11.
What is a sonic boom ?
Q 12.
What is acoustical transite ?
Q 13.
What is a wave number?
Q 14.
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 15.
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.
Q 16.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 17.
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
Q 18.
Fill in the blanks :
Waves transport _________ not matter.
Q 19.
Fill in the blanks :
Sound having frequency less than 20Hz is known as ___________.
Q 20.
A ship sends out ultrasound that returns from the seabed and is detected after 3.42 s.If the speed of the ultrasound through sea water is 1531 m/s,what is the distance of the seabed from the ship ?
Q 21.
Distinguish between loudness and intensity of sound.
Q 22.
is sound wave called a longitudinal wave ?
Q 23.
What is reverberation ? How can it be reduced ?
Q 24.
Draw a curve showing density or pressure variations with respect to distance for a disturbance produced by sound.Mark the position of compression and rarefaction on this curve.Also define wavelengths and time period using this curve.
Q 25.
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 26.
Distinguish between music and noise.
Q 27.
Why sound waves are called mechanical waves?
Q 28.
What type of waves can travel in vacuum? Give example(s).
Q 29.
Give examples of organisms which can hear infrasonic?
Q 30.
A sound wave has a frequency of 2
kHz and wavelengtl 35 cm.How long will it take to travel 1.5 km ?
Q 31.
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 32.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is 440 m/s in a given medium.
Q 33.
What is the audible range of the average human ear ?
Q 34.
Describe with the help of a diagram,how compressions and rarefactions are produced in air near a source of sound.
Q 35.
Explain how defects in a metal block can be detected using ultrasound.
Q 36.
What is persistence of hearing ?
Q 37.
We see flash earlier than the thunder.Discuss.
Q 38.
Deaf people can be made to dance to music.Explain how ?
Q 39.
What travels faster : a rifle bullet or the sound of the shot fired from it ?
Q 40.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 41.
Give examples of longitudinal waves.
Q 42.
Can sound wave travel in vacuum?
Q 43.
Distinguish between loudness and intensity of sound.
Q 44.
Calculate the wavelength of a sound wave having a frequency 300 Hz and speed 330 m/s.
Q 45.
The sonic boom of an aircraft has a time period of 0 00005 s.Calculate the frequency of the sound produced.
Q 46.
A child hears an echo from a cliff 4 s after the sound of a pwerful cracker is produced.How far away is the cliff from the child ? (Take speed of sound in air as 340 m/s)
Q 47.
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 48.
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 49.
Why are sound waves called mechanical waves ?
Q 50.
What are wavelength,frequency,time period and amplitude of a sound wave ?
