Two waves of nearly same amplitude , same frequency travelling with same velocity are superimposing to give phenomenon of interference . If `a_(1)` and `a_(2)` be their respectively amplitudes , `omega` be the frequency for both , `v` be the velocity for both and `Delta phi` is the phase difference between the two waves then ,

Options

A. The resultant intensity varies periodically with time and distance
B. The resultant intensity with `I_(min)/(I_(max)) = ((a_(1) - a_(2))/(a_(1) + a_(2)))^(2)` is obtained for coherent waves travelling in the same direction.
C. Both the waves must have constant phase difference at any point all the time.
D. `I _(R) = I_(1) + I_(2) + 2sqrt(I_(1)I_(2)) cos (Delta phi))`, where constructive interference is obtained for path differences that are odd for path differences that are even multiple of `(1)/(2)lambda`

Answer

B, C

Explanation

For interference of the waves, these must be travelling in same directions and coherent and the relation of maximum and minimum intensities is already explained in article6.7.1