Question:
What travels faster : a rifle bullet or the sound of the shot fired from it ?
Answer:
Modem rifles are able to impart a velocity of about 900 m/s to a bullet which is about three times more than the speed of sound in air (340 m/s).Even if we take into account the air friction which retards the bullet,it still travels faster than sound.Thus,a bullet would have hit its victim before the sound of the shot reaches his ear.
Sound
Q 1.
What are the factors speed of sound wave depends upon?
Q 2.
What are ultrasonics?
Q 3.
What is a wave number?
Q 4.
How are compressions and rarefactions produced near a source of sound ?
Q 5.
How is sound propagated through a material medium ? What is wave motion ?
Q 6.
What is infrasonic? Give an example.
Q 7.
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 8.
Fill in the blanks :
The product of wavelength of wave and its frequency gives _____________.
Q 9.
Fill in the blanks :
v = ? × ?
Q 10.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 11.
A hospital uses an ultrasonic scanner to locate tumors in a tissue. What is the wavelength of sound in a tissue is which the speed of sound is 1.7 km/s. The operating frequency of the scanner is 4.2 MHz. (1MHz = 10
6 Hz).
Q 12.
What is audible range ?
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.
Fill in the blanks :
Waves transport _________ not matter.
Q 15.
What type of waves can travel in vacuum? Give example(s).
Q 16.
Explain how sound is produced by your school bell ?
Q 17.
What propagates along with the waves ?
Q 18.
Deaf people can be made to dance to music.Explain how ?
Q 19.
What is speed of sound in air?
Q 20.
Three persons, A, B and C are made to hear a sound travelling through different mediums as given below:
| Persons | Medium |
| A | Iron Rod |
| B | Air |
| C | Water |
Who will hear the sound first? Why?
Q 21.
How are the wavelength and frequency of a sound wave related to its speed?
Q 22.
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 23.
Give an application use of ultrasonics.
Q 24.
What type of wave is represented by density- distance graph?
Q 25.
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 27.
Why do we use upholstered seats in theatres and halls ?
Q 28.
Fill in the blanks :
In a __________ wave the particles of the medium oscillate in a direction perpendicular to the direction in which the wave propagates.
Q 29.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 30.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 31.
What is reverberation?
Q 32.
What is Sound? Why it is important for us?
Q 33.
Guess which sound has a higher pitch: guitar or car horn?
Q 34.
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 35.
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 36.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 37.
Explain the working and application of a sonar.
Q 38.
How can you show that sound waves are longitudinal waves ?
Q 39.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 40.
Fill in the blanks :
A ________ (pulse/wave) is a disturbance which is sudden and lasts for a short duration of time.
Q 41.
Fill in the blanks :
If the time interval between original sound and reflected sound is more than 1/10 second then original sound and reflected sound can be heard clearly. This reflected sound is known as _______.
Q 42.
What are wavefronts?
Q 43.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is
440 m/s in a given medium.
Q 44.
A person is listening to a tone of 500 Hz sitting at a distance of 450 m from the source of the sound. What is the time interval between successive compressions from the source?
Q 45.
Distinguish between loudness and intensity of sound.
Q 46.
Calculate the wavelength of a sound wave having a frequency 300 Hz and speed 330 m/s.
Q 47.
A sound wave has a frequency of 2
kHz and wavelengtl 35 cm.How long will it take to travel 1.5 km ?
Q 48.
A man fires a gun towards a hill and hears its echo after 5 s.He then moves 340 m towards the hill and fires his gun again.This time he hears the echo after 3 s.Calculate the speed of sound.
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 is the audible range of the average human ear ?
