Question

In the following figure S1 and S2 are coherent sources. The intensity of both sources is the same. If the intensity at the point P is 4W/m^2, What is the intensity of each source?

Answer 1

I am at a loss about how you expect me to respond when I can not see the figure. If the distances are the same, the amplitude of the waves add to become 2a if they started at a and the intensity is A^2 = 4 a^2. Of couse if the difference were half a wavelength they would cancel.