Question

A plane sound wave traveling with velocity 'v' in a medium A reaches a point on the interface of medium A and medium B. If velocity of sound in medium B is $2v$, the angle of incidence for total internal reflection of the wave will be greater than ($\sin {30}^o=0.5$ and $\sin {90}^o=1$).

• A. ${15}^o$
• B. ${30}^o$
• C. ${45}^o$
• D. ${90}^o$

Answer 1

Answer: (B)

${30}^o$

For total internal reflection,
$\sin i>\frac{1}{\mu }$
Using $\mu =\frac{v_B}{v_A}=\frac{2v}{v}=0.5$
$\therefore$ $\sin i>0.5$
Or $i>{\sin }^{-1}\left(0.5\right)$
$⟹i>{30}^o$