Question

Explain reflection at the boundary of a denser medium.

Answer 1

1. A longitudinal wave travels in a medium in the form of compressions and rarefactions. Suppose a compression travelling in the air from left to right reaches a rigid wall.
2. The compression exerts a force F on the rigid wall. In turn, the wall exerts an equal and
   opposite reaction R = -F on the air molecules. This results in a compression near the rigid wall.
3. Thus, a compression travelling towards the rigid wall is reflected back as a compression. That is the direction of compression is reversed.
   
   Reflection of sound at a denser medium