A rectangular glass slab ABCD of refractive index is immersed in water of refractive index n2 (n1

Question

A rectangular glass slab ABCD of refractive index is immersed in water of refractive index n₂ (n₁ > n₂). A ray of light is incident at surface AB of the slab as shown. The maximum value of the angle of incidence α_max, such that the ray comes out only from the other surface CD, is giiven by

Accepted Answer

Rays come out only from CD, means rays after refraction from AB get total internally reflected at AD.
From figure
    r₁ + r₂ = 90^o
∴   r₁ = 90^o - r₂
      (r₁)_max = 90^o - (r₂)_min and
      (r₂)_min = θ_c (For total internal reflection at AD)
Where, sin θ_c =

or θ_c = sin^-1

∴ (r₁)_max = 90^o - θ_c
Now applying Snellâ€™s law at face AB

or sin α_max =

cosθ_C
∴ α_max = sin^-1

Question

Options

Solution

More Geometrical Optics Questions