Question

Critical angle of glass is $\theta_{1}$ and that of water is $\theta_{2}$. The critical angle for water and glass surface would be $\left(\mu_{g}=3 / 2, \mu_{w}=4 / 3\right)$

• A. between $\theta_{1}$ and $\theta_{2}$
• B. greater than $\theta_{2}$
• C. less than $\theta_{1}$
• D. less than $\theta_{2}$

Answer 1

Answer: (B)

Here, $\sin \theta_{1}=\frac{1}{\mu_{g}}=\frac{1}{3 / 2}=0.6666$
and $\sin \theta_{2}=\frac{1}{\mu_{w}}=\frac{1}{4 / 3}=\frac{3}{4}=0.75$
As $\mu_{g}>\,\mu_{w}$,
$ \therefore \theta_{1}<\,\theta_{2}$
If $\theta$ is the critical angle between glass and water, then
$\sin \theta=\frac{\mu_{w}}{\mu_{g}}=\frac{4 / 3}{3 / 2}=\frac{8}{9}=0.8888$
$\therefore \theta>\,\theta_{2}$