Question:
Why do we use upholstered seats in theatres and halls ?
Answer:
Upholstered scats are those which are fitted with padding,springs and covering.Such seats absorb sound and improve the acoustics of the halls and the theatres.Moreso,such seats eliminate,to a large extent,the dependence on audience for absorption of sound.
Sound
Q 1.
What are the factors speed of sound wave depends upon?
Q 2.
What is audible range ?
Q 3.
What is speed of sound in air?
Q 4.
What are ultrasonics?
Q 5.
How is sound propagated through a material medium ? What is wave motion ?
Q 6.
How are compressions and rarefactions produced near a source of sound ?
Q 7.
What is a wave number?
Q 8.
What is infrasonic? Give an example.
Q 9.
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 10.
How are the wavelength and frequency of a sound wave related to its speed ?
Q 11.
What propagates along with the waves ?
Q 12.
How does sound travel in gases and liquids as longitudinal or as transverse waves?
Q 13.
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 14.
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 16.
Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is
440 m/s in a given medium.
Q 17.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 18.
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 19.
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 20.
Fill in the blanks :
v = ? × ?
Q 21.
If 20 waves are produced per second, what is the frequency in hertz?
Q 22.
Give an application use of ultrasonics.
Q 23.
Which wave characteristics determine the
(a) Loudness (b) pitch of sound?
Draw two different waveforms and mark these characteristics on it.
Q 24.
Explain how sound is produced by your school bell ?
Q 25.
Why are sound waves called mechanical waves ?
Q 26.
By how much does the speed of sound increase with rise of temperature ?
Q 27.
Why do we use upholstered seats in theatres and halls ?
Q 28.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 29.
What is a mechanical wave?
Q 30.
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 31.
What type of wave is represented by density- distance graph?
Q 32.
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 33.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 34.
Fill in the blanks :
A ________ (pulse/wave) is a form of disturbance which travels through a medium as a result of repetitive oscillations of the particles of the medium.
Q 35.
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 36.
Fill in the blanks :
Ripples waves on water surface are example of ____________.
Q 37.
Fill in the blanks :
In a _____________ wave the particles of the medium oscillate in the direction in which the wave travels.
Q 38.
Fill in the blanks :
Full form of SONAR is __________________________.
Q 39.
Why sound waves are called mechanical waves?
Q 40.
How does the sound produced by a vibrating object in a medium reach your ear?
Q 41.
An observer standing at the sea coast observes 54 waves reaching the coast per minute.If the wavelength of a wave is 10 m,find the wave velocity.
Q 42.
The frequency of a source of sound is 100 Hz.How many times does it vibrate in a minute ?
Q 43.
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 44.
Fill in the blanks :
In the case of a ___________ wave, distance between two consecutive condensations or rarefactions is known as wavelength.
Q 45.
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 46.
Can sound wave travel in vacuum?
Q 47.
What type of waves can travel in vacuum? Give example(s).
Q 48.
Why transverse wave does not travel through air or gases?
Q 49.
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 50.
A sound wave has a frequency of 2
kHz and wavelengtl 35 cm.How long will it take to travel 1.5 km ?
