NCERT Class 9 Science — Chapter 5: Sound

mcqeasy

Which of the following correctly represents the order of speed of sound ($v$) in different media?

Official previous-year question

Verified 1 Aug 2026.

Options

A$v_{liquid} > v_{solid} > v_{gas}$
B$v_{solid} > v_{liquid} > v_{gas}$
C$v_{solid} > v_{gas} > v_{liquid}$
D$v_{gas} > v_{liquid} > v_{solid}$

Did you get this right?

Solution

The correct option is

$v_{solid} > v_{liquid} > v_{gas}$

Explanation

Sound is a mechanical longitudinal wave that propagates through a medium via the vibration of particles. The speed of sound ($v$) in a medium is governed by the properties of that medium, specifically its elasticity (modulus of elasticity, $E$) and density ($\rho$), according to the relationship $v = \sqrt{\frac{E}{\rho}}$.

Analysis:

Solids: Particles in solids are tightly packed, and the intermolecular forces are very strong. This results in high elasticity. Although solids are denser than gases, their high modulus of elasticity dominates, allowing sound waves to travel fastest through them.
Liquids: The particles are less tightly packed compared to solids, and the intermolecular forces are weaker. Consequently, the speed of sound in liquids is lower than in solids but higher than in gases.
Gases: Particles in gases are far apart and have negligible intermolecular forces. Gases have the lowest elasticity among the three states of matter, resulting in the slowest propagation of sound.

For instance, the speed of sound is approximately 5,960 m/s in steel (solid), 1,482 m/s in water (liquid), and 343 m/s in air (gas).

Key Takeaway:

The speed of sound follows the order: Solid > Liquid > Gas, primarily because the elasticity of solids is significantly higher than that of liquids and gases.

Your note

More from Chapter 5: Sound

Consider the following statements regarding the propagation of sound: 1. The disturbance created by a source travels through the medium to the listener. 2. Sound waves are characterized as non-mechanical waves. 3. A material medium is mandatory for the transmission of sound. Which of the statements given above are correct?

medium

With reference to the characteristics of a sound wave, consider the following statements: 1. The distance between two consecutive compressions is called the wavelength. 2. The time taken for one complete oscillation is called the frequency. 3. The SI unit of frequency is Hertz. Which of the statements given above are correct?

medium

Consider the following statements regarding Ultrasound: 1. It refers to sounds with frequencies higher than 20 kHz. 2. Ultrasound waves scatter immediately when they encounter obstacles. 3. Ultrasound is incapable of penetrating metal blocks to detect flaws. Which of the statements given above is/are correct?

easy

The cleaning action of an ultrasonic cleaner is primarily achieved through:

medium

With reference to medical applications of sound, consider the following statements: 1. Echocardiography uses ultrasonic waves to form an image of the heart. 2. Ultrasonography uses X-rays to detect stones in the gall bladder. 3. Ultrasound can be used to break kidney stones into fine grains. Which of the statements given above are correct?

medium

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The correct option is

$v_{solid} > v_{liquid} > v_{gas}$

Explanation

Analysis:

Solids: Particles in solids are tightly packed, and the intermolecular forces are very strong. This results in high elasticity. Although solids are denser than gases, their high modulus of elasticity dominates, allowing sound waves to travel fastest through them.
Liquids: The particles are less tightly packed compared to solids, and the intermolecular forces are weaker. Consequently, the speed of sound in liquids is lower than in solids but higher than in gases.
Gases: Particles in gases are far apart and have negligible intermolecular forces. Gases have the lowest elasticity among the three states of matter, resulting in the slowest propagation of sound.

For instance, the speed of sound is approximately 5,960 m/s in steel (solid), 1,482 m/s in water (liquid), and 343 m/s in air (gas).

Key Takeaway:

The speed of sound follows the order: Solid > Liquid > Gas, primarily because the elasticity of solids is significantly higher than that of liquids and gases.