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Physics [3 Mark Question Answer]

Sound · ICSE STD 10 (ICSE - English Medium). 15 questions.

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[3 Mark Question Answer]

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Question 13 Marks
Shows the wave patterns of three sounds A, B and C. Name the characteristic of sound which is same between (i) A and B, (ii) B and C, and (iii) C and A.
Answer

(i) Since both have same amplitude and waveform therefore loudness and quality is same.

(ii) Neither amplitude nor waveform is same. Hence no characteristic is same.

(iii) Frequency of both the sound is same in this case hence pitch is same.

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Question 23 Marks
Name three characteristics of a musical sound.
Answer
The following three characteristics of sound are:
(i) Loudness
(ii) Pitch or shrillness
(iii)Quality or timber.
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Question 33 Marks
Draw a diagram to show the wave pattern of high pitch note and a low pitch note, but of the same loudness.
Answer


The first diagram is high pitch note and second one is low pitch note.
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Question 43 Marks
The bells of a temple are big in size. Why?
Answer

According to the study of bells (called campanology), larger bells provide less resonant frequency.

For a sound wave to travel long distances, it is essential that the frequency of the sound is less.

Also, it is observed that thicker the body of a bell, richer is the quality of sound.

This is the reason the bells of a temple are big in size.

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Question 53 Marks
State three factors on which loundess of sound heard by a listener depends.
Answer
The loudness of the sound heard depends on:
(i) Loudness is proportional to the square of the amplitude.
(ii) Loudness is inversely proportional to the square of distance.
(iii)Loudness depends on the surface area of the vibrating body.
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Question 63 Marks
When a body vibrates under a periodic force, the vibrations of the body are:

  • natural vibrations

  • Damped vibrations

  • Forced vibration

  • Resonant vibrations

Answer
Forced vibrations

Hint: The vibrations of a body which take place under the influence of external periodic force acting on it are called the forced vibrations.

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Question 73 Marks
(a) Name one factors on which the frequency of sound emitted due to vibrations in an air column depends.

(b) How does the frequency depend on the factor stated in part (a).

Answer
The frequency of sound emitted due to vibration in an air column depends on the length of the air column.
The factor which influences the frequency of sound is the length of the air column.
As the length of the air column increases, the frequency decreases.
Thus, we can conclude that they are inversely proportional to each other.
f $\alpha \frac{1}{\iota}$
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Question 83 Marks
Name the phenomenon involved in tuning your radio set to a particular station and define it.
Answer
The phenomenon involved is resonance. It is a special case of forced vibrations. When the frequency of an externally applied periodic force on a body is equal to its natural frequency, the body rapidly begins to vibrate with an increased amplitude. This phenomenon is known as resonance.
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Question 93 Marks
When a troop crosses a suspension bridge the soldiers are asked to break steps. Explain the reason.
Answer
When a troop crosses a suspension bridge, the soldiers are asked to break steps. The reason is that when soldiers march in steps, all the separate periodic forces exerted by them are in same phase and therefore forced vibrations of a particular frequency are produced in the bridge. Now, if the natural frequency of the bridge happens to be equal to the frequency of the steps, the bridge will vibrate with large amplitude due to resonance and suspension bridge could crumble.
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Question 103 Marks
Differentiate between the forced and resonant vibrations.
Answer
Forced Vibrations Resonant vibrations
These are vibrations of a body under an external periodic force of frequency different than the natural frequency of the body. These are vibrations of a body under an external periodic force of frequency exactly equal to the natural frequency of the body.
The amplitude of the vibration is usually small. The amplitude of vibration is very large.
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Question 113 Marks
On keeping the stem of a vibrating tuning fork on the surface of a table, a loud sound is heard. Give reason.
Answer

A loud sound is heard only when a special case of forced vibration (resonance) has occurred.

When the frequency of the periodic force applied on a body is equal to the natural frequency of that body, we hear a loud soundcalled resonance.

It is due to resonance that a loud sound is heard on keeping the stem of a vibrating tuning fork on the surface of a table.

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Question 123 Marks
The following diagram shows three ways in which the string of an instrument can vibrate.



(a) which of the diagram shows the principal note?
(b) which has the frequency four times that of the first?
(c) what is the ratio of the frequency of the vibration in (i) and (ii)?
Answer
(a) (i) Diagram is showing the principal note.
(b) (iii)Diagram has frequency four times that of the first.
(c) Ratio is 1:2
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Question 133 Marks
A pendulum has a frequency of 5 vibrations per second. An observer starts the pendulum and fires a gun simultaneously. He hears echo from the cliff after 8 vibrations of the pendulum. If the velocity of sound in air is 340 m s-1, find the distance between the cliff and the observer.
Answer
5 vibrations by pendulum in 1 sec
So 8 vibrations in 8/5 seconds = 1.6 sec
Velocity = 2 × D/ time
340 = 2 × D/ 1.6
D = 340 × 1.6 / 2 = 272 m
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Question 143 Marks
How do bats avoid obstacles in their way, when in flight?
Answer
Bats can produce and detect the sound of very high frequency up to about 1000kHz. The sounds produced by flying bats get reflected back from any obstacle in front of it. By hearing the echoes, bats come to know even in the dark where the obstacles are. So they can fly safely without colliding with the obstacles.
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Question 153 Marks
Explain how the speed of sound can be determined by the method of echo.
Answer
Sound is produced from a place at a known distance say, $d$ at least $50 m$ from the reflecting surface. The time interval $t$ in which the echo reaches the place from where the sound was produced, is noted by a stop watch having the least count $0.01 s$. then the speed of sound is calculated by using the following relation $V =$ total distance travelled $/$ time interval $=\frac{2 d}{t} m / s$
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[3 Mark Question Answer] - Physics STD 10 Questions - Vidyadip