# When light of a creation wavelength is incident an a plane surface of a material at a glancing angle 30°, the reflected light is found to be completely plane polarized determine…

Q: When light of a creation wavelength is incident an a plane surface of a material at a glancing angle 30°, the reflected light is found to be completely plane polarized determine.
(a) refractive index of given material and
(b) angle of refraction.

Sol: (a) Angle of incident light with the surface is 30°. The angle of incidence = 90° – 30° = 60°. Since
reflected light is completely polarized, therefore incidence takes place at polarizing angle of incidence
ip.

∴ ip = 60°

Using Brewster’s law ,

? = tan ip

? = tan 60° = √3

(b) From Shell’s law

$\large \mu = \frac{sini}{sinr}$

$\large \sqrt{3} = \frac{sin60^o}{sinr}$

$\large sinr = \frac{sin60^o}{\sqrt{3}} = \frac{\sqrt{3}}{2 \times \sqrt{3}}$

or sin r = 1/2,

r = 30°