Question

Two coherent monochromatic light beams of intensities I and 4I are supperposed. The maximum and minimum possible intensities in the resulting beams are

(a) 5I and I 

(b) 9I and I 

(c) 5I and 3I 

(d) 9I and 3I

Answer 1

(b) 9I and I 

I_max = \(({\sqrt I_1}+{\sqrt I_2})^2\) = (  \(({\sqrt 41}+{\sqrt I})^2\)) = 9I 

I_max = \(({\sqrt I_1}+{\sqrt I_2})^2\) = (  \(({\sqrt 41}+{\sqrt I})^2\)) = I