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For a partially polarized light beam, the degree of polarization is defined as P = (I_max - I_min) / (I_max + I_min). If P = 0.25 for a given beam, find the approximate ratio of maximum to minimum amplitudes in the two mutually perpendicular directions.

1. 4
2. 1.66
3. 1.3
4. 9

Correct answer: 1.3

Solution

From P = (I_max - I_min)/(I_max + I_min) = 0.25, let r = I_max/I_min. Then (r-1)/(r+1) = 0.25, giving r = 5/3. Amplitude ratio = sqrt(I_max/I_min) = sqrt(5/3) approximately 1.29 approximately 1.3.

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