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

Options

A. `4I and I
B. `5I and 3I
C. 9I and I
D. 9I and 3I

Answer

C

Explanation

`I_(max)/I_(min)=((sqrt(I_(1))+sqrt(I_(2)))/(sqrt(I_(1))~sqrt(I_(2))))^(2)=((sqrt(I)+sqrt(4I))/(sqrt(I)~sqrt(4I)))^(2)=9/1`
`I_(max)=9I, I_(min)=I`