Question

Explain the reflection of sound waves at
the surface of (1) a denser medium (2) a rarer
medium.​

Answer 1

$\huge\underline{\underline\mathtt{Answer:-}}$

(1)$\bf\large\underline\red{Reflection \:from \:a \:denser \:medium :-}$

consider a sound wave incident on a denser medium such as a rigid wall. When a compression is incident on the wall, the particles of air close to the wall are in a compressed state. To return to their normal condition, the particles begin to press in the opposite direction and therefore a compression gets reflected as a compression and a rarefaction is reflected as a rarefaction. However, the displacements of the particles in the reflected wave are opposite to their displacements in the incident wave, so that there is a change of phase of 180° or a radians.

2)$\bf\large\underline\red{Reflection \:from \:a \:rarer \:medium :-}$ When sound waves are reflected from the surface of a rarer medium, there is no change of phase. Therefore, a compression is reflected as a rarefaction and vice versa. The reason is as follows:

When a compression is incident on the surface of a rarer medium, it can pass into that medium. This is because the particles of the rarer medium are free to move and they get compressed, leaving a rarefaction behind, which travels in the opposite direction. In a similar manner an incident rarefaction gets reflected as a compression