Question

When sound waves travel from a rarer medium to a denser medium, its speed:

• A. decreases
• B. remain constant
• C. increases
• D. may increase or decrease

Answer 1

The correct option is D may increase or decrease

The speed of sound is dependent on the density and elasticity of a medium. The speed of sound decreases with increase in density. But since it is also dependent on the elasticity of the medium, on varying density, the speed might increase or decrease.
For example when a sound wave travels from air to steel, steel is denser than air, so the speed should decrease. But since steel is more elastic when compared to air, the speed increases.