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.
Why do we use upholstered seats in theatres and halls ?
Q 3.
Fill in the blanks :
v = ? × ?
Q 4.
What propagates along with the waves ?
Q 5.
What is a wave number?
Q 6.
What are ultrasonics?
Q 7.
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 8.
Explain how sound is produced by your school bell ?
Q 9.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 10.
How is sound propagated through a material medium ? What is wave motion ?
Q 11.
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 12.
Explain how the human ear works.
Q 13.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 14.
What are wavefronts?
Q 15.
Calculate the wavelength of a sound wave having a frequency 300 Hz and speed 330 m/s.
Q 16.
What is infrasonic? Give an example.
Q 17.
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 18.
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 19.
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 20.
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 21.
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
Q 22.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 23.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 24.
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 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.
Deaf people can be made to dance to music.Explain how ?
Q 27.
What travels faster : a rifle bullet or the sound of the shot fired from it ?
Q 28.
What type of wave is represented by density- distance graph?
Q 29.
Explain the working and application of a sonar.
Q 30.
What is audible range ?
Q 31.
Guess which has a higher pitch : a guitar or a car horn ?
Q 32.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 33.
What is reverberation ? How can it be reduced ?
Q 34.
Write the name of the wave which propagates in terms of compressions and rarefactions.
Q 35.
How are compressions and rarefactions produced near a source of sound ?
Q 36.
What do you mean by reverberation and reverberation time ? How is reverberation controlled ?
Q 37.
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 38.
Can sound wave travel in vacuum?
Q 39.
Distinguish between loudness and intensity of sound.
Q 40.
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 41.
How does the sound produced by a vibrating object in a medium reach your ear ?
Q 42.
What is the audible range of the average human ear ?
Q 43.
On what factors does the speed of sound in a material depend ?
Q 44.
Fill in the blanks :
Waves transport _________ not matter.
Q 45.
Fill in the blanks :
Audible sound range is _________ to _____________.
Q 46.
How are the wavelength and frequency of a sound wave related to its speed?
Q 47.
Give an application use of ultrasonics.
Q 48.
When you shout in front of a hill,your own shout is repeated.Explain.
Q 49.
Can you produce sound without utilizing energy ?
