A ray of light intensity I is incident on a parallel glass-slab at a point `A` as shown in figure. It undergoes partial reflection and refraction. At each reflection `25%` of incident energy is reflected. The rays `AB` and `A^(')B^(')` undergo interference. The ratio `I_(max)//I_(min)` is

Options

A. (a) `4:1`
B. (b) `8:1`
C. (c) `7:1`
D. (d) `49:1`

Answer

D

Explanation

From figure `I_1=I/4` and `I_2=(9I)/(64)impliesI_2/I_1=9/16`

By using `I_(max)/I_(min)=((sqrt(I_2/I_1)+1)/(sqrt(I_2/I_1)-1))=((sqrt(9/16)+1)/(sqrt(9/16)-1))=49/1`