The two light beams having intensities I and 9 I interfere to produce a fringe pattern on a screen. The phase difference between the beams is π 2 at point P and π at point Q . Then the difference between the resultant intensities at P and Q will be :

Step-by-step solution

Resultant intensity is given by, I resultant = I 1 + I 2 + 2 I 1 I 2 cos ϕ At P , I P = 9 I + I + 2 9 I × I cos π 2 = 10 I At Q , I Q = 9 I + I + 2 9 I × I cos π = 10 I - 2 × 3 I = 4 I Now, difference between intensities is 10 I - 4 I = 6 I