Sound Class 7: Assertion and Reason Questions

Practise important assertion and reason questions on vibrations, sound production, pitch, loudness, the human voice, hearing and noise pollution. Select an option, check your answer and read the explanation.

20 Exam Questions Instant Answer Check Detailed Explanations Mobile Friendly

A vibrating tuning fork producing compressions and rarefactions in air — A vibrating tuning fork produces sound by disturbing the surrounding air.

Quick Revision Before You Begin

These core ideas will help you solve the questions accurately.

Sound and Vibrations

Sound is produced when an object vibrates. The vibration makes particles of the surrounding medium move back and forth.

Material Medium

Sound needs a medium such as a solid, liquid or gas. It cannot travel through an empty vacuum.

Loudness

Loudness is mainly related to the amplitude of vibration. A larger amplitude generally produces a louder sound.

Pitch

Pitch is related to frequency. A faster vibration has a higher frequency and produces a higher-pitched sound.

How to Answer Assertion and Reason Questions

First decide whether the assertion is true. Then decide whether the reason is true. Finally check whether the reason correctly explains the assertion.

Option A: Both statements are true, and the reason correctly explains the assertion.

Option B: Both statements are true, but the reason does not correctly explain the assertion.

Option C: The assertion is true, but the reason is false.

Option D: The assertion is false, but the reason is true.

Sound Assertion and Reason Practice Set

Attempt every question before opening its explanation.

Production of Sound

Assertion: A ringing school bell produces sound because it vibrates.

Reason: Vibrations are repeated to-and-fro motions of an object about its mean position.

A. Both statements are true, and the reason correctly explains the assertion. B. Both statements are true, but the reason does not correctly explain the assertion. C. The assertion is true, but the reason is false. D. The assertion is false, but the reason is true.

Correct option: A. The bell moves rapidly to and fro after being struck. These vibrations disturb the surrounding air and produce sound.

Sound in Vacuum

Assertion: Sound cannot travel through a vacuum.

Reason: Sound needs particles of a material medium to carry the disturbance from one place to another.

Correct option: A. A vacuum has no material particles. Therefore, there are no particles to pass the sound disturbance forward.

Plucked String

Assertion: A plucked guitar string stops producing sound when it stops vibrating.

Reason: The vibrating string is the source of the sound.

Correct option: A. The string produces sound only while it is vibrating. Once its vibration dies away, it no longer creates sound waves.

Loudness and Amplitude

Assertion: A drum usually sounds louder when it is struck harder.

Reason: Striking it harder generally produces vibrations of greater amplitude.

Correct option: A. Greater amplitude means a stronger vibration, which normally produces a louder sound.

Pitch and Frequency

Assertion: A rapidly vibrating object produces a higher-pitched sound than a slowly vibrating object.

Reason: Pitch increases when the frequency of vibration increases.

Correct option: A. Frequency is the number of vibrations made in one second. A higher frequency is heard as a higher pitch.

Human Voice

Assertion: The human voice is produced in the larynx.

Reason: Air from the lungs can make the vocal cords in the larynx vibrate.

Correct option: A. The larynx contains two vocal cords. Air passing through the narrow gap between them makes them vibrate and produce sound.

Voice Pitch

Assertion: A child's voice is generally higher-pitched than an adult man's voice.

Reason: A child's vocal cords are generally longer and thicker than an adult man's vocal cords.

Correct option: C. The assertion is true. Children's vocal cords are generally shorter and thinner, so they vibrate faster and produce a higher pitch.

Sound Through Matter

Assertion: Sound can travel through solids, liquids and gases.

Reason: Particles in each of these media can pass the sound disturbance to neighbouring particles.

Correct option: A. Solids, liquids and gases all contain particles. Vibrations can be transferred from particle to particle through these media.

The Eardrum

Assertion: The eardrum vibrates when sound reaches the ear.

Reason: Sound waves create changing pressure that pushes and pulls on the eardrum.

Correct option: A. The pressure changes in a sound wave make the thin eardrum move back and forth.

Music and Noise

Assertion: Both musical sounds and noise are produced by vibrating sources.

Reason: Every vibrating source always produces a pleasant musical sound.

Correct option: C. Vibrations produce both musical sounds and noise. However, not every vibration produces a pleasant or musical sound.

Mosquito Sound

Assertion: A mosquito can produce a high-pitched sound that is not very loud.

Reason: Pitch and loudness are different characteristics of sound.

Correct option: A. High pitch comes from rapid vibration, while loudness depends mainly on amplitude. A sound can therefore be high-pitched but soft.

Amplitude and Pitch

Assertion: Increasing the amplitude of vibration always increases the pitch of a sound.

Reason: Amplitude mainly affects the loudness of sound.

Correct option: D. Greater amplitude generally makes a sound louder, not higher-pitched. Pitch mainly depends on frequency.

Meaning of Frequency

Assertion: A higher frequency means fewer vibrations are completed in one second.

Reason: Frequency is the number of vibrations completed in one second.

Correct option: D. Higher frequency means more vibrations, not fewer vibrations, are completed in one second.

Tabla Membrane

Assertion: A tabla produces sound when its stretched membrane is struck.

Reason: Striking the membrane sets it into vibration.

Correct option: A. The stretched membrane vibrates after being struck and causes the surrounding air to vibrate.

Sound from the Sun

Assertion: Sound produced on the Sun can travel directly through space and reach Earth.

Reason: Sound requires a material medium for propagation.

Correct option: D. Most of the space between the Sun and Earth is nearly a vacuum, so ordinary sound waves cannot travel directly through it.

Buzzing of Insects

Assertion: The buzzing of many flying insects is connected with the rapid movement of their wings.

Reason: Rapid wing movement creates vibrations and disturbances in the surrounding air.

Correct option: A. The rapid wing motion repeatedly disturbs the air, producing the buzzing sound.

Tuning Fork in Water

Assertion: A vibrating tuning fork can splash water when its prongs touch the water surface.

Reason: The vibrating prongs transfer motion to the water.

Correct option: A. The splashing makes the tuning fork's vibration visible because its moving prongs push the water repeatedly.

Frequency and Loudness

Assertion: Loudness depends only on the frequency of vibration.

Reason: Frequency mainly determines whether a sound has a high or low pitch.

Correct option: D. Loudness mainly depends on amplitude, while frequency mainly affects pitch.

Quality of Sound

Assertion: Two musical instruments can sound different even when they play sounds of the same pitch and similar loudness.

Reason: Different instruments can produce different sound qualities because their vibrations are not identical in form.

Correct option: A. Sound quality helps us distinguish the same note played by different instruments, even when pitch and loudness are similar.

Noise Pollution and Hearing

Assertion: We should avoid prolonged exposure to very loud sounds.

Reason: Long or repeated exposure to loud sound can damage hearing.

Correct option: A. Very loud sound can harm the sensitive structures of the ear, especially when exposure continues for a long time or occurs repeatedly.

Exam Tips for Assertion and Reason Questions

Use this three-step method during revision and examinations.

Check Each Statement Separately

Do not decide the option after reading only the assertion. Test the truth of both statements independently.

Look for Cause and Effect

A true reason is not always the correct explanation. Ask whether it directly tells why the assertion is true.

Revise Key Pairs

Remember amplitude with loudness, frequency with pitch, vibration with sound production, and medium with sound travel.

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Frequently Asked Questions

Sound is produced by a vibrating object. The vibrations create disturbances in a surrounding material medium.

A vacuum has no material particles to transfer the vibration, so ordinary sound waves cannot propagate through it.

Loudness is mainly related to amplitude, while pitch is mainly related to frequency.

Air from the lungs passes through the larynx and makes the vocal cords vibrate, producing sound.

A higher frequency means that more vibrations are completed each second, producing a higher-pitched sound.

Check whether each statement is true, then decide whether the reason directly and correctly explains the assertion.

Sound Class 7 Assertion and Reason Questions with Answers