Question:
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.
Answer:
(i) A buzzing fly informs us the presence of a nuisance.Had it not buzzed,we would have paid it no mind.
(ii) The lawn mower’s putt-putt tells us that our neighbour has finaly got around to cleaning up the jungle in his garden - disappearance of a nuisance.
(iii) The sound of a teakettle informs us that the time has come for a coffee break-presence of refreshment.
Thus,these sounds arouse various emotions -anger at the fly,satisfaction that your neighbour has ultimately got across the hint to clean the forest,and desire for coffee.
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 are ultrasonics?
Q 6.
What is a wave number?
Q 7.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 8.
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 9.
Explain how sound is produced by your school bell ?
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.
How is sound propagated through a material medium ? What is wave motion ?
Q 12.
What are wavefronts?
Q 13.
Explain how the human ear works.
Q 14.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 15.
What is infrasonic? Give an example.
Q 16.
Calculate the wavelength of a sound wave having a frequency 300 Hz and speed 330 m/s.
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.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 20.
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 21.
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 22.
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
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.
What is audible range ?
Q 26.
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 27.
Deaf people can be made to dance to music.Explain how ?
Q 28.
What travels faster : a rifle bullet or the sound of the shot fired from it ?
Q 29.
What type of wave is represented by density- distance graph?
Q 30.
Explain the working and application of a sonar.
Q 31.
How are compressions and rarefactions produced near a source of sound ?
Q 32.
Can sound wave travel in vacuum?
Q 33.
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 34.
Guess which has a higher pitch : a guitar or a car horn ?
Q 35.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 36.
What is reverberation ? How can it be reduced ?
Q 37.
Write the name of the wave which propagates in terms of compressions and rarefactions.
Q 38.
What do you mean by reverberation and reverberation time ? How is reverberation controlled ?
Q 39.
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 40.
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 41.
Fill in the blanks :
Waves transport _________ not matter.
Q 42.
How are the wavelength and frequency of a sound wave related to its speed?
Q 43.
Distinguish between loudness and intensity of sound.
Q 44.
How does the sound produced by a vibrating object in a medium reach your ear ?
Q 45.
Distinguish between loudness and intensity of sound.
Q 46.
What is the audible range of the average human ear ?
Q 47.
On what factors does the speed of sound in a material depend ?
Q 48.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 49.
Fill in the blanks :
RADAR (Radio Detection And Ranging) works on _____________ principle which is used to determine the velocities and movement of aircrafts.
Q 50.
Fill in the blanks :
Full form of SONAR is __________________________.
