1. The problem statement, all variables and given/known data 1) At a given point in space, the total light wave is composed of 3 phasors P1 = a, P2 = (a/2)e^(i(theta)), P3 = (a/2)e^(-i(theta)). What is the intensity of light at this point? 2. Relevant equations 3. The attempt at a solution I solved it in the following way: P = P1 + P2 + P3 = a + (a/2)e^(i(theta)) + (a/2)e^(-i(theta)) = a + (a/2)[cos(theta) + isin(theta) + cos(theta) - isin(theta)] = a + acos(theta) = 2acos^2(theta/2) I = P^2 = 4a^2cos^4(theta/2) But if P3 = ae^(-i(theta)) then this method won’t work, isn’t it? So could someone suggest a more general way to solve such problems?