Sound Test

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Sound Test - 5

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Weekly Quiz Competition

Question 1
1 / -0

In which of the following materials is the speed of sound maximum?

A
Air

B
Sea water

C
Fresh water

D
Steel

Solution

The speed of sound is maximum in steel among the given substances. The speed of sound depends upon the elastic behaviour of the medium. The greater the elasticity of the medium, the greater the speed of the sound.
Question 2
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If two men talk on the Moon's surface, then

A
they hear each other with lower frequency

B
they hear each other with higher frequency

C
they can only hear each other

D
they can't hear each other at all

Solution

There is no atmosphere on Moon, so sound cannot travel in vacuum. Hence, they can't hear each other at all.
Question 3
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Read the following statements and choose the correct option accordingly.

Statement A: We can produce sound by changing the pressure of the air in the instrument.
Statement B: To produce sound, we have to do a certain mechanical work.

A
Both statements are correct.

B
Statement A is correct, but statement B is incorrect.

C
Statement A is incorrect, but statement B is correct.

D
Both statements are incorrect.

Solution

When we vibrate an object, a certain mechanical work has to be done. For example, we have to do a certain work for striking a tuning fork so that its prongs start vibrating.
When a vibrating object moves forward, it pushes and compresses the air in front of it creating a region of high pressure. This region is called a compression. This compression starts to move away from the vibrating object. When the vibrating object moves backwards, it creates a region of low pressure called rarefaction. As the object moves back and forth rapidly, a series of compressions and rarefactions is created in the air.
These make the sound wave that propagates through the medium. Compression is the region of high pressure and rarefaction is the region of low pressure.
Question 4
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Note is a sound

A
of mixture of several frequencies

B
of mixture of two frequencies only

C
of a single frequency

D
always unpleasant to listen

Solution

A sound that is produced when several frequencies are mixed is called a note. For example, a musical note has tones of various frequencies (sounds of different pitches) and amplitudes (loudness). Usually, the loudest is called the fundamental. The higher frequency harmonics are called overtones which are the integer multiple of the fundamental frequency.
Question 5
1 / -0

Read the following statements and choose the correct option accordingly.

Statement A: During the propagation of a sound wave, particles oscillate to and fro about their mean positions.
Statement B: For the propagation of sound, the medium should be elastic in nature.

A
Both statements are correct.

B
Statement A is correct, but statement B is incorrect.

C
Statement A is incorrect, but statement B is correct.

D
Both statements are incorrect.

Solution

Mechanical waves can be produced only in media which possess elasticity and inertia. Sound is a mechanical wave, so it requires a medium which is elastic in nature.
When an object vibrates, it sets the particles of the medium around it vibrating. The particles do not travel all the way from the vibrating object to the ear. A particle of the medium in contact with the vibrating object is first displaced from its equilibrium position. It then exerts a force on the adjacent particle. As a result, the adjacent particle gets displaced from its position of rest. After displacing the adjacent particle, the first particle comes back to its original position. This process continues in the medium so the particle starts oscillating about their mean positions along the direction of the propagation of wave.
Question 6
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Two sounds A and B are of frequencies f and 2f, respectively. Which of the following is correct?

A
B is grave, A is shrill.

B
B is shrill, A is grave.

C
Both sounds are identical.

D
B is louder than A.

Solution

Sound B is shrill and A is grave because the frequency of B is more than that of A. The greater the frequency of the sound, the greater the shrillness in sound.
Question 7
1 / -0

Loudness of a sound is determined by the ________ of vibration.

A
frequency

B
amplitude

C
wavelength

D
velocity

Solution

Loudness of a sound is proportional to the square of the amplitude of the wave.
Question 8
1 / -0

Two sounds of same loudness and same pitch produced by two different instruments differ in their

A
frequencies

B
amplitudes

C
waveforms

D
All of the above

Solution

The waveform of a sound depends on the number of the overtones and their relative amplitudes along with the fundamental frequency. The resultant vibration obtained by the superposition of all these vibrations gives the waveform of sound.
Question 9
1 / -0

Study the following graphs and choose the correct option.

A
Wave B has a higher pitch than wave A.

B
Waves A and B have same pitch.

C
Wave A has a higher pitch than wave B.

D
None of the above

Solution

Wave A has a higher pitch than wave B, as wave A has completed 2 complete cycles and wave B has completed 1 cycle in the same duration.
Question 10
1 / -0

Read the following statements and choose the correct option accordingly.

Statement A: If the length of a string is increased, the pitch of the sound will also increase.
Statement B: The pitch of the sound is independent of the length of the string.

A
Both statements are correct.

B
Statement A is correct, but statement B is incorrect.

C
Statement A is incorrect, but statement B is correct.

D
Both statements are incorrect.

Solution

The pitch of the sound is proportional to the frequency of the sound. The greater the frequency, the higher the pitch.
The frequency of the sound is inversely proportional to the square root length. The greater the length, the lesser the frequency.
So, both the statements are wrong.
Question 11
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Before playing the orchestra in a musical concert, a sitarist tries to adjust the tension and pluck the strings suitably. By doing so, he is adjusting the

A
intensity of sound only

B
amplitude of sound only

C
frequency of the sitar strings with the frequency of other musical instruments

D
loudness of sound

Solution

The pitch of the sound is proportional to the frequency of the sound. The greater the frequency, the higher the pitch.
The frequency of the sound is proportional to the square root of the tension. The greater the tension, the greater the frequency.
So, we can say that when a sitarist tries to adjust the tension and pluck the strings suitably, by doing so he is adjusting the frequency of the sitar strings with the frequency of other musical instruments.
Question 12
1 / -0

Fill in the blanks:

The outer ear, called ______, receives sound from the surroundings. This sound passes to the ________ through the auditory canal. At the end of the auditory canal, there is a thin membrane called ______ or tympanic membrane. The eardrum is forced to vibrate due to pressure variations in the air. A set of bones in the middle ear amplifies these vibrations of the eardrum and forwards these to the inner ear. Then, these vibrations are converted into electrical signals by _______.

A
pinna, eardrum, middle ear, cochlea

B
pinna, middle ear, eardrum, cochlea

C
pinna, eardrum, cochlea, middle ear

D
cochlea, pinna, ear drum, cochlea

Solution

The pinna is the only visible part of the ear with its special helical shape. It is the first part of the ear that reacts with sound. The function of the pinna is to act as a kind of funnel which assists in directing the sound further into the ear.
The middle ear is the part of the ear between the eardrum and the oval window. The middle ear transmits sound from the outer ear to the inner ear. The middle ear consists of three bones (i.e. the hammer (malleus), the anvil (incus) and the stirrup (stapes)), the oval window, the round window and the Eustachian tube.
The eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit sound from the air to the ossicles inside the middle ear and then to the oval window in the fluid-filled cochlea.
The function of the cochlea is to transform the vibrations of the cochlear liquids and associated structures into a neural signal. These signals are then passed to the auditory nerve and carried up to the brain.
Question 13
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Sound waves are sent from a submarine and received back after 5 seconds. At what distance may the enemy submarine be present? (The speed of sound in water is 1500 m/.)

A
3500 m

B
3550 m

C
3700 m

D
3750 m

Solution

Let the distance between the submarine and the receiver be d.
Distance travelled by the sound = 2d
Now, Speed = Distance/Time
Question 14
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Arjun stands at point A, fires a shot, whose sound travels in air with a speed of 300 m/s. How long after the firing of shot will Rahul, standing at point B, hear its echo?

A
1 s

B
2 s

C
3 s

D
4 s

Solution

Distance travelled by the sound from A to B = d = 300 m
Time taken by the sound to travel from A to B = t₁ = d/v = 300/300 = 1 s
Distance travelled by the sound from point B to again point B after reflection from the cliff = 2d = 600 m
Time taken by the sound in this = t₂= 2d/v = 600/300 = 2 s
Total time taken to hear the echo from the time of firing = t₁+ t₂ = 1 + 2 = 3 s
Question 15
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The wavelength, i.e. the distance between two consecutive crests or troughs of a wave is 2 m and the velocity of the wave is 440 m/s. What will be the frequency?

A
220 hertz

B
440 hertz

C
880 hertz

D
110 hertz

Solution

As speed = wavelength × frequency
Question 16
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A source of wave produces 40 crests and 40 troughs in 0.6 seconds.

The frequency of the wave is

A
100 Hz

B
40 Hz

C
333 Hz

D
67 Hz

Solution

Number of crests and troughs in one cycle is 1 each.
Frequency = Number of crests/Time
Number of crests = 40, Time = 0.6 sec
Question 17
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Eardrum vibrations are amplified several times by three bones in the middle ear. These bones are

A
hammer, anvil and stirrup

B
hammer, cochlea and pinna

C
hammer, cochlea and stirrup

D
cochlea, pinna and stirrup

Solution

At the end of the auditory canal, there is a thin membrane called eardrum or tympanic membrane. Eardrum is forced to vibrate due to pressure vibrations in air. A set of bones in the middle ear (hammer, anvil and stirrup) amplify these vibrations of the eardrum and forward these to the inner ear.
Hence, option (1) is correct.
Question 18
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An ear converts pressure variations in the air with audible frequencies into electrical signals and these signals travel to the brain through the ___________.

A
eustachian tube

B
tympanic membrane

C
oval window

D
auditory nerve

Solution

Eardrum is made to vibrate due to pressure variations in air. Bones in the middle ear amplify these vibrations of the eardrum and forward these to inner ear. Then, these vibrations get converted into electrical signals by cochlea. An electrical signal is sent to the brain through the auditory nerve and is interpreted as sound. Hence, option (4) is correct.
Question 19
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An echo returns in 0.3 s. What is the distance of the reflecting surface from the source of sound?
(Speed of sound = 344 ms^-1)

A
114.6 m

B
103.2 m

C
93.5 m

D
51.6 m

Solution

Here, time taken by an echo to return = 0.3 s
So, 2d = v × t
2d = 344 × 0.3
2d = 103.2
or, d = 51.6 m
Distance of the reflecting surface from the source of sound is 51.6 m
Hence, option (4) is correct.
Question 20
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Two sound waves travelling in the same medium have time periods in the ratio 3 : 5. The ratio of their speeds is

A
3 : 5

B
5 : 3

C
1 : 1

D
3 : 8

Solution

Speed of sound depends upon the nature of the medium and the temperature of surroundings. As two sound waves travel in the same medium under same conditions, their speeds will be same. So, the ratio of their speeds is equal to 1 : 1. Hence, option (3) is correct.