If the ratio of the intensity of two coherent sources is 4 then the visibility `[(I_(max)-I_(min))//(I_(max)+I_(min))]` of the fringes is

Options

A. 4
B. 4/5
C. 43529
D. 9

Answer

B

Explanation

Given `(I_(1))/(I_(2))=4thereforeI_(1)=4I" (let the "I_(2)=I`)
`I_(max)=(sqrt(I_(1))+sqrt(I_(2)))^(2)=(2sqrt(I)+sqrt(I))^(2)=9I`
`I_(min)=(sqrt(I_(1)-sqrt(I_(2)))^(2)=(2sqrt(I)-sqrt(I))^(2)=I`
`therefore(I_(max)-I_(min))/(I_(max)+I_(min))=(9I-I)/(9I+I)=(81)/(101)=(4)/(5)`