Question

The critical angle of a certain medium is $\sin ^{-1}\left(\frac{4}{5}\right)$. The polarising angle of medium is

• A. $\tan ^{-1}\left(\frac{5}{4}\right)$
• B. $\sin ^{-1}\left(\frac{4}{5}\right)$
• C. $\sin ^{-1}\left(\frac{5}{4}\right)$
• D. $\tan ^{-1}\left(\frac{4}{3}\right)$

Answer 1

Answer: (A)

Here, Critical angle, $i_{c}=\sin ^{-1}\left(\frac{4}{5}\right)$
$\therefore \quad \sin i_{c}=\frac{4}{5}$
As $\mu=\frac{1}{\sin i_{c}}=\frac{5}{4}$
According to Brewster's law,
$\tan i_{p}=\mu$
where, $i_{p}$ is the polarising angle
$\therefore \tan i_{p}=\frac{5}{4}$
$\Rightarrow i_{p}=\tan ^{-1}\left(\frac{5}{4}\right)$