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.
Why do we use upholstered seats in theatres and halls ?
Q 2.
What are the factors speed of sound wave depends upon?
Q 3.
Fill in the blanks :
v = ? × ?
Q 4.
What are ultrasonics?
Q 5.
What propagates along with the waves ?
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.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 8.
Explain how sound is produced by your school bell ?
Q 9.
How is sound propagated through a material medium ? What is wave motion ?
Q 10.
What is a wave number?
Q 11.
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 12.
Explain how the human ear works.
Q 13.
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 14.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 15.
What are wavefronts?
Q 16.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 17.
What is infrasonic? Give an example.
Q 18.
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 19.
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 20.
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 21.
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 22.
Calculate the wavelength of a sound wave having a frequency 300 Hz and speed 330 m/s.
Q 23.
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 24.
What is the audible range of the average human ear ?
Q 25.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 26.
Explain the working and application of a sonar.
Q 27.
What is audible range ?
Q 28.
Try to imagine what you would feel, what sort of person you would be,had you been born totally deaf.
Q 29.
What type of wave is represented by density- distance graph?
Q 30.
Guess which has a higher pitch : a guitar or a car horn ?
Q 31.
What travels faster : a rifle bullet or the sound of the shot fired from it ?
Q 32.
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 33.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 34.
Write the name of the wave which propagates in terms of compressions and rarefactions.
Q 35.
Can sound wave travel in vacuum?
Q 36.
When you shout in front of a hill,your own shout is repeated.Explain.
Q 37.
What is persistence of hearing ?
Q 38.
What is the minimum distance of the obstacle from the source of sound for hearing distinct echo ?
Q 39.
What is the difference between an echo and a reverberation ?
Q 40.
Deaf people can be made to dance to music.Explain how ?
Q 41.
What is Sound? Why it is important for us?
Q 42.
What type of waves can travel in vacuum? Give example(s).
Q 43.
Why transverse wave does not travel through air or gases?
Q 44.
If 20 waves are produced per second, what is the frequency in hertz?
Q 45.
Give an application use of ultrasonics.
Q 46.
Distinguish between loudness and intensity of sound.
Q 47.
The sonic boom of an aircraft has a time period of 0 00005 s.Calculate the frequency of the sound produced.
Q 48.
A sound wave has a frequency of 2
kHz and wavelengtl 35 cm.How long will it take to travel 1.5 km ?
Q 49.
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 50.
What are wavelength,frequency,time period and amplitude of a sound wave ?
