Question

The interference pattern is obtained with two coherent light sources of intensity ratio n. In the interference patten, the ratio `(I_(max)-I_(min))/(I_(max)+I_(min))` will be
A. (a) `(sqrtn)/((n+1)^2)`
B. (b) `(2sqrtn)/((n+1)^2)`
C. (c) `(sqrtn)/(n+1)`
D. (d) `(2sqrtn)/(n+1)`

Answer 1

Correct Answer - D
Let `I_1/I_2=n/1`
`(I_(max)-I_(min))/(I_(max)+I_(min))=((sqrtI_1+sqrtI_2)^2-(sqrtI_1-sqrtI_2)^2)/((sqrtI_1+sqrtI_2)^2(sqrtI_1-sqrtI_2)^2)`
`=(4sqrt(I_1I_2))/(2(I_1+I_2))`
Dividing numberator and denomenator by `I_2`, required ratio
`=(2sqrt(I_1//I_2))/((I_1/I_2+1))=(2sqrtn)/(n+1)`