devarshi-dt-logo

Question:

In an interference, the intensity of two interfering waves are I and 4I respectively. They produce intensity at two points A and B with phase angle of π/2 and π respectively. Then difference in intensity between them is.

2I

5I

4I

I

Solution:

Net intensity after interference of waves with phase difference φ:
Inet = I1 + I2 + 2√(I1I2)cosφ
Thus
Inet1 (φ = π/2) = 5I
Inet2 (φ = π) = I
Thus, the difference between them = 4I