Two coherent sources produce intensities 4I and I separately at a point P. The two waves arrive at P exactly out of phase. If the resultant intensity is NI, find N.
Physics · Wave Optics · interferece of light and huygen principle
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Question

Two coherent sources produce intensities 4I and I separately at a point P. The two waves arrive at P exactly out of phase. If the resultant intensity is NI, find N.

G1 Physics · Accepted Answer

Let amplitude a correspond to intensity I. Then the amplitudes are 2a and a. For a phase difference of π, the amplitudes subtract: a(resultant) = 2a−a = a. Thus, I(resultant) = I. Hence N = 1.