Question

If the gas is lighter than air, sound waves are refracted

• A. away from the normal
• B. towards the normal
• C. total internal reflection
• D. not sufficient data

Answer 1

The correct option is A away from the normal

The refraction phenomenon occurs whenever waves travel from one medium to another in which the velocity of the wave changes. The amount of refraction at the media interface obeys Snell's law.
Sound waves travel more slowly when they pass from a lighter to a heavier gas. So, the sound wave travels more faster when it passes from heavier to lighter medium and, hence bends away from the normal.
If the gas is lighter than air, the sound waves are refacted away from the normal.