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**1. Homework Statement**

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. Homework 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?