Question:
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.
Answer:
We know that loudness is directly proportional to the density of the medium.The density of ground is much higher than that of air.Thus,the sound of distant horses,when conveyed through ground,is louder than when through air.Therefore,by applying ear to the ground,we can hear this sound.But when the ear is a little distance above the ground,the sound travels through air and is hardly audible.
Sound
Q 1.
What are the factors speed of sound wave depends upon?
Q 2.
Fill in the blanks :
v = ? × ?
Q 3.
Why do we use upholstered seats in theatres and halls ?
Q 4.
What propagates along with the waves ?
Q 5.
Explain how sound is produced by your school bell ?
Q 6.
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 7.
Explain how the human ear works.
Q 8.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 9.
What is a wave number?
Q 10.
What are ultrasonics?
Q 11.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 12.
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 13.
Calculate the wavelength of a sound wave having a frequency 300 Hz and speed 330 m/s.
Q 14.
What are wavefronts?
Q 15.
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 16.
Fill in the blanks :
Waves transport _________ not matter.
Q 17.
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 18.
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 19.
How is sound propagated through a material medium ? What is wave motion ?
Q 20.
Can sound wave travel in vacuum?
Q 21.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 22.
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 23.
Write the name of the wave which propagates in terms of compressions and rarefactions.
Q 24.
Deaf people can be made to dance to music.Explain how ?
Q 25.
What travels faster : a rifle bullet or the sound of the shot fired from it ?
Q 26.
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
Q 27.
Fill in the blanks :
Audible sound range is _________ to _____________.
Q 28.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 29.
What is infrasonic? Give an example.
Q 30.
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 31.
Radio Ceylon broadcasts at 25 m.What is the frequency of the station ?
Q 32.
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 33.
How does the sound produced by a vibrating object in a medium reach your ear ?
Q 34.
Distinguish between loudness and intensity of sound.
Q 35.
What is the audible range of the average human ear ?
Q 36.
Discuss the role of medium in the propagation of sound.
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.
Fill in the blanks :
RADAR (Radio Detection And Ranging) works on _____________ principle which is used to determine the velocities and movement of aircrafts.
Q 39.
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 40.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 41.
Does sound follow the same laws of reflection as light does ? Explain.
Q 42.
What is reverberation ? How can it be reduced ?
Q 43.
What is sound ? Discuss the method of its production.
Q 44.
How are compressions and rarefactions produced near a source of sound ?
Q 45.
What are transverse waves ?
Q 46.
On what factors does the speed of sound in a material depend ?
Q 47.
Today our life is richer and fuller of music than it was yesterday,and much of this is due to progress in engineering.What will happen to human feelings when the sea of knowledge spreads further ?
Q 48.
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 49.
Fill in the blanks :
Number of oscillations completed by the oscillator in one second is known as ___________.
Q 50.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
