Question

Interference pattern is obtained on a screen due to two identical sources of monochromatics light. The intensity of the central brigh fringe is I when one of the two sources is blocked, its intensity becomes `I_(0)`. The intensity in two situations are related as
A. `I=I_(0)`
B. `I= sqrt(2).I_(0)`
C. `I= 2 I_(0)`
D. `I= 4I_(0)`

Answer 1

Correct Answer - D
`I=I_(1)+I_(2)+sqrt(I_(1)I_(2))= 2 cos (alpha_(1)-alpha_(2))`
For bright fringe, `(alpha_(1)-alpha_(2))=0 and I_(1)=I_(2) =I_(0)`
`:. I=I_(0)+I_(0)+2 sqrt(I_(0)I_(0))=4I_(0)`