Interference fringes are produced on a screen by using two light sources of intensities I and 9 I . The phase difference between the beams is π 2 at the point P and π at the point Q on the screen. The difference between the resultant intensities at point P and Q is

Step-by-step solution

At point P, resultant intensity of interfering wave is I P r e s = I 1 + I 2 + 2 I 1 I 2 cos ⁡ θ For θ = π 2 , I P r e s = I + 9 I = 10 I At point Q, resultant intensity of interfering wave is I Q r e s = 10 I - 2 . 9 I 2 = 10 I - 6 I = 4 I for θ = π ∴ ∆ I = I P r e s - I g r e s = 10 I - 10 I + 6 I = 6 I