Two sources of intensity `I` and 4I are used in an interference experiment. Find the intensity at a point where the waves from two sources superimpose with a phase difference of (a) zero, (b) `pi//2`, (c ) `pi` and (d) ratio of maximum and minimum intensity.

Explanation

In case of interference of two waves of intensities `I_1 and I_2` with phase difference `phi`
`I_R = I_1 +I_2 + 2 (sqrt(I_1I_2)) cos phi`
Here, `I_1 = I and I_2 = 4I`,
`I_R =I + 4I + 2sqrt(4I xx I) cos phi = 5I + 4I cos phi`
So, (a) For `phi =0,I_R =5I + 4I xx I =9I[as cos -0 =1]`
(b) For `phi =(pi//2),I =5I [cos phi =(pi//2) =0]`
( c) For `phi =pi, I =5I + 4I (-1) = I [as cos (pi) =-1]`