Question:
If you set your watch by the sound of a distant siren, will it go fast or slow ?
Answer:
Sound from the distant siren takes time to reach us.Thus,our watch becomes slow by as much time as the time taken by sound to reach us.For example,if the siren sounds 1.30 pm and sound takes 3 seconds to reach us,our watch which has been set after listening to the siren at 1.30 pm is slower by 3 seconds.
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 are ultrasonics?
Q 5.
What propagates along with the waves ?
Q 6.
What is a wave number?
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.
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 11.
Explain how the human ear works.
Q 12.
How is sound propagated through a material medium ? What is wave motion ?
Q 13.
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 14.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 15.
What are wavefronts?
Q 16.
What is infrasonic? Give an example.
Q 17.
Calculate the wavelength of a sound wave having a frequency 300 Hz and speed 330 m/s.
Q 18.
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 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.
What travels faster : a rifle bullet or the sound of the shot fired from it ?
Q 27.
What type of wave is represented by density- distance graph?
Q 28.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 29.
Explain the working and application of a sonar.
Q 30.
What is audible range ?
Q 31.
Deaf people can be made to dance to music.Explain how ?
Q 32.
Can sound wave travel in vacuum?
Q 33.
Guess which has a higher pitch : a guitar or a car horn ?
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.
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 :
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.
Distinguish between loudness and intensity of sound.
Q 39.
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 40.
How does the sound produced by a vibrating object in a medium reach your ear ?
Q 41.
What is the audible range of the average human ear ?
Q 42.
What is reverberation ? How can it be reduced ?
Q 43.
What is persistence of hearing ?
Q 44.
What do you mean by reverberation and reverberation time ? How is reverberation controlled ?
Q 45.
Fill in the blanks :
Waves transport _________ not matter.
Q 46.
Fill in the blanks :
Audible sound range is _________ to _____________.
Q 47.
How are the wavelength and frequency of a sound wave related to its speed?
Q 48.
If 20 waves are produced per second, what is the frequency in hertz?
Q 49.
Give an application use of ultrasonics.
Q 50.
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.
