Question

When a wave is reflected from a denser medium, the change in phase is

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

Answer 1

Answer: (B)

When a wave is reflected from a denser medium, the wave is reversed both in its direction and amplitude.
$\therefore$ in the time domain there is a change of phase of $\pi$
$y=a\sin (Kx-\omega t)$ $y_r=-a\sin (Kx+\omega t)$
in time domain $y_r=+a\sin (\omega t+\pi )$
$\therefore$ phase difference is $\pi$