Question

Sound waves cannot travel through which of the following mediums?

• A. Solids
• B. Liquids
• C. Gases
• D. Vacuum

Hint:

Sound requires particles to carry vibrations. Solid ✓ Liquid ✓ Gas ✓ Vacuum ✗ Therefore, outer space is essentially silent.

Answer 1

The Correct Option is D

Concept: Sound is a mechanical wave. Unlike electromagnetic waves such as light, mechanical waves require a material medium for propagation. The movement of particles in the medium enables the transfer of sound energy.

Step-by-Step Analysis:

• Why Sound Requires a Medium Sound travels through successive compressions and rarefactions. For this process to occur:

• Particles must be present.

• These particles must vibrate.

• Vibrations must be transferred from one particle to another.
Without particles, sound cannot propagate.

• Vacuum (Correct Answer) A vacuum contains no material particles.

• No molecules are present.

• No collisions can occur.

• No compressions or rarefactions can be formed.

• Therefore, sound cannot travel through a vacuum.
This principle explains why astronauts in outer space cannot hear one another directly without communication devices.

• Solids (Option A) Sound travels very efficiently through solids because particles are closely packed. Examples:

• Iron

• Steel

• Wood
In fact, sound travels fastest in solids.

• Liquids (Option B) Sound can travel through liquids because molecules are present and capable of transmitting vibrations. Example:

• Sound travels effectively through water.

• Marine animals such as whales communicate using sound waves underwater.

• Gases (Option C) Sound commonly travels through gases. Example:

• Human speech travels through air.

• Air acts as the medium between speaker and listener.
Although sound travels through gases, its speed is lower than in liquids and solids.
The general relationship is: \[ V_{\text{solid}} > V_{\text{liquid}} > V_{\text{gas}} \] Thus, the only medium through which sound cannot travel is a

vacuum.