Two beams of ligth having intensities I and 4I interface to produce a fringe pattern on a screen. The phase difference between the beams is `(pi)/(2)` at point A and `pi` at point B. Then the difference between the resultant intensities at A and B is

Options

A. `2I`
B. `4I`
C. `5I`
D. `7I`

Answer

B

Explanation

Resultant intensity `I_(R)=I_(1)+I_(2)+2sqrt(I_(1)I_(2))cosphi`
`I_(A)=5I and I_(B)=I`
`:.` The difference between the intensity `I_(A)-I_(B)=4I`