Question

A sound wave travels from air to water. The angle of incidence is $\alpha_{1}$ and the angle of refraction is $\alpha_{2}$. Assuming Snell's law to be valid.

• A. $\alpha_{2}<\alpha_{1}$
• B. $\alpha_{2}>\alpha_{1}$
• C. $\alpha_{2}=\alpha_{1}$
• D. $\alpha_{2}=90^{\circ}$

Answer 1

Answer: (B)

$\mu_{1} \sin \alpha_{1}=\mu_{2} \sin \alpha_{2}$
$\Rightarrow \frac{v_{w}}{v_{\text {air }}} \sin \alpha_{1}=\frac{v_{\text {air }}}{v_{\text {air }}} \sin \alpha_{2}$
or $\sin \alpha_{2}=\frac{v_{ w }}{v_{\text {air }}} \sin \alpha_{1}$
As $v_{w}>v_{\text {air }} ; \alpha_{2}>\alpha_{1}$