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. 5I and I
B. 5I and 3I
C. 9I and I
D. 9I and 3I

Answer

C

Explanation

`I_(max)=I+4I+2sqrt(Ixx4I)=9I`,
and `I_(min)=I+4I-2sqrt(Ixx4I)=I`.