# ICSE Class 9th Physics – Sound MCQs

#### The maximum displacement suffered by the particles of a medium about their mean position is called ____.

Correct! Wrong!

The maximum displacement suffered by the particles of the medium about their mean position is called amplitude.

#### An electric vibrator produces ripples in a ripple tank, such that the distance between one crest and one trough is 2 cm. If the vibrations are produced at a rate of 4800 per minute. Then, the time period is ____ s.

Correct! Wrong!

The time period of the wave is 0.0125 s.

#### Longitudinal waves can travel in ____.

Correct! Wrong!

Longitudinal wave can travel in solids, liquids and gases.

#### SONAR is the technique based on the principle of reflection of sound.

Correct! Wrong!

SONAR - sound navigation and ranging is the technique based on the principle of reflection of sound.

#### Ultrasonic waves are those waves which a human being can hear.

Correct! Wrong!

Ultrasonic waves are sound waves with a frequency greater than 20 kHz, which is not audible to human being.

#### Echo is produced due to the resonance of sound.

Correct! Wrong!

Echo is produced due to reflection of sound.

#### The voice of ladies is shrill because of ____.

Correct! Wrong!

That property of voice which we call pitch is determined by the rate of vibration of the vocal cords. The greater the number of vibrations per second, the higher the pitch. The rate of vibration, in turn, is determined by the length and thickness of the vocal cords and by the tightening or relaxation of these cords. Normally, women's voices are pitched higher than men's because women's vocal cords are shorter.

#### The characteristic of a sound, which distinguishes a feeble sound from a loud sound of the same frequency is called ____.

Correct! Wrong!

The characteristic of a sound which distinguishes a feeble sound from a loud sound of the same frequency is called loudness.

#### An echo is heard in 0.4 s, if the speed of sound is 330 m/s, then the distance of the reflecting surface is ____ m.

Correct! Wrong!

The distance of the reflecting surface is 66 m.

#### Which of the following frequencies of sound waves are audible to human beings?

Correct! Wrong!

Frequency of 5,000 cycles/second is in the audible range of 20 Hz - 20,000 Hz. Hence, only 5000 cycles/second frequency is audible to human beings.

#### The average amount of energy passing through a unit area per unit time in a specified direction is called ____ of the wave.

Correct! Wrong!

Intensity of the wave is defined as the average amount of energy passing through a unit area per unit time in a specified direction.

#### SONAR is based on the principle of resonance.

Correct! Wrong!

Sonar (which started as an acronym for sound navigation and ranging) is a technique that uses sound propagation (usually underwater) to navigate, communicate or to detect other vessels. SONAR is based on the principle of echo.

#### The velocity of sound in air is not affected by change in ____.

Correct! Wrong!

Atmospheric pressure does not affect the velocity of sound.

#### A sound wave propagating through a medium has bounced back into the same medium by hitting a hard surface and then such a phenomenon is called ____ of sound.

Correct! Wrong!

A sound wave propagating through a medium has bounced back into the same medium by hitting a hard surface and then such a phenomenon is called reflection of sound.

#### Among the following properties of a wave, the one that is independent of the other is its ____.

Correct! Wrong!

The maximum displacement of the particle from its mean position is defined as amplitude where the wave is independent of it.

#### When the particles of the medium vibrate perpendicular to the propagation of the wave, then the wave is called ____ wave.

Correct! Wrong!

In transverse wave, particles of the medium vibrate perpendicular to the propagation of the wave.

#### Which of the following devices, does not work on the principle of multiple reflection of sound?

Correct! Wrong!

Gramophone does not work on the principle of multiple reflection of sound. Devices like megaphone, bulb horn, stethoscope and soundboards work on the principle of multiple reflection of sound.

#### The kind of motion in which transfer of energy takes place when the particles move about their mean position is called ____ motion.

Correct! Wrong!

When a disturbance is created in an elastic medium, it is transferred from one particle to another particle in the form of a wave. This type of propagation is known as wave motion.

#### If the frequency of a sound wave is doubled, its wavelength ____.

Correct! Wrong!

If the frequency of a wave is doubled, its wavelength becomes halved.

#### The speed of sound at 0 °C is 330 m/s. Then, the speed of sound at a temperature of 20 °C is ____ m/s.

Correct! Wrong!

For 1 °C rise in temperature, the increase in speed is 0.6 m/s For 20 °C rise in temperature, the increase in speed is 0.6 × 20 = 12 m/s Speed of sound at 20 °C is 330 + 12 Speed of sound at 20 °C is 342 m/s.

#### A boy stands at a distance of 25 m from a cliff. He shoots a rifle and hears the echo at the end of 0.5s. The velocity of sound in air is ____ m/s.

Correct! Wrong!

The velocity of sound in air is 100 m/s.

#### The distance between two consecutive crests or troughs is defined as ____.

Correct! Wrong!

The distance between two consecutive crests or troughs is defined as wave length.

#### The time taken by a particle of a medium to complete one vibration is called ____.

Correct! Wrong!

Time taken by a particle of medium to complete one vibration is called time period.

#### Human ear can perceive sounds ranging from ____.

Correct! Wrong!

Human ear cannot perceive sounds of all frequencies; it can perceive sounds ranging from 20 Hz to 20,000 Hz.

#### The wave in which the individual particles of a medium oscillate along the direction of wave propagation is called ____.

Correct! Wrong!

The wave in which the individual particles of the medium oscillate along the direction of wave propagation is called longitudinal wave.

#### A wave of wavelength 0.56 cm is produced in air and it travels at a speed of 320 m/s. Then, the frequency is ____ Hz and it is ____.

Correct! Wrong!

As, the frequency is more than 20000 Hz, it is not audible.

#### The vibrations of frequency greater than 20,000 Hz are called ____ vibrations.

Correct! Wrong!

The vibrations of frequency greater than 20,000 Hz, which a human ear cannot perceive are known as ultrasonic vibrations.

#### An echo is a phenomenon of reflection of sound from an obstacle

Correct! Wrong!

An echo is a phenomenon of reflection of sound from an obstacle.

#### Human ear can hear a sound of wavelength ____ m.

Correct! Wrong!

Human ear can hear a sound of wavelength, 17 m.

#### Which of the following devices, work on the principle of multiple reflection of sound?

Correct! Wrong!

Stethoscope works on the principle of multiple reflection of sound.

ICSE Class 9th Physics - Sound MCQs
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