Question

Image of sun formed due to reflection at air water interface is found to be very highly polarised. Refractive index of water being $\mu =4/3$, find the angle of sun above the horizon.

• A. ${34.7}^{\circ }$
• B. ${36.9}^{\circ }$
• C. ${33.3}^{\circ }$
• D. ${53.8}^{\circ }$

Answer 1

The correct option is B ${36.9}^{\circ }$

Since the reflected light is very highly polarised, it implies that incident light falls at polarising angle of incidence ${\theta }_P$. From Brewster’s law,
$\mu =\tan {\theta }_P$
$\therefore {\theta }_P={\tan }^{-1}\left(\mu \right)={\tan }^{-1}\left(4/3\right)={53.1}^{\circ }$
Since ${\theta }_P$ is the angle which the rays from sun make with the normal to the interface, angle with the interface will be ${90}^{\circ }–{53.1}^{\circ }={36.9}^{\circ }$.