Question

The phase change between incident and reflected sound wave from a fixed wall is

• A. 0
• B. $\pi$
• C. $3\pi$
• D. $2\pi$

Answer 1

Answer: (B)

$\pi$

Answer 2

When a wave is reflected from a wall, the wave is inverted. As the phase difference between a wave and its inverted wave is $\bar{n}$, the phase difference is $\pi$ $y=A \cos (k x+\omega t)$ $y_{r}=-A \cos (k x+\omega t)$ $=A \cos (k x+\omega t+\pi)$ $\Rightarrow \phi=\pi$