JEE Main201912 Jan 2019Morning ShiftPhysicsRay OpticsActual
A light wave is incident normally on a glass slab of refractive index 1.5 . If 4 % of light gets reflected and the amplitude of the electric field of the incident light is 30 V m , then the amplitude of the electric field for the wave propagating in the glass medium will be:
Options
- A30 V m
- B6 V m
- C24 V m
- D10 V m
Correct answer
C. 24 V m
Step-by-step solution
n = refractive index = ε r μ r I = 1 2 ε 0 E 0 2 C I ′ = 1 2 ε E 2 V I ′ = 0.96 I 1 2 ε E 2 v = 0.96 1 2 ε 0 E 0 2 C E = 0.96 ε 0 ε 0 ε r c v E 0 (For most of the transparent medium μ r ≈ 1 ) ⇒ E = 0.96   .   1 ε r μ r .   c v E 0 = 0.96 . 1 n .   n   E 0 E = 0.96 n   E 0 E = 0 . 96 1 . 5 × 30 = 24   V m