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
$\sin \theta =\frac{{\mu }_w}{{\mu }_g}=\frac{4/3}{3/2}=\frac{8}{9}=0.8888$
$\therefore \theta >{\theta }_2$