Question

When light of wavelength (lambda)falls on a plane surface
of a material at glancing angle 30°, the reflected light
is plane polarized and transmitted light is partially
polarized. Refractive index of given material is
(1) √2
(2)1/root 2
(3) √3
(4)1/root3

Answer 1

Answer:

1/root 3

Explanation:

since angle formed is 30

tan 30 is to be taken

and the result is 1/root3

Answer 2

Hence the refractive index of the given material is  1 /√3

Option (4) is correct.

Explanation:

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 θp.

∴θp = 60∘

Using Brewster's law

μ = tanθ p=tan 60∘

μ = √ 3

b) Form Snell's law

μ = sini / sinr

∴√3 = sin 60∘ / sinr

sinr = √3 / 2 × 1 / √3

Hence the refractive index of the given material is  1 /√3