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

`I_(A)=I+4I+2sqrt(4I^(2))cos((pi)/(2))=5I`
`I_(B)=I+4I+2sqrt(4I^(2))cospi=I`
So difference `I_(A)-I_(B)=4I`