Two coherent monochromatic light beams of intensities I and 4 I 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

Let `I_1=I and I_2=4I ` I_max=(sqrtI_1+sqrt_2)^2=(sqrt+sqrt4I)^2=(3sqrtI)^2=9I`
`I_min=(sqrtI_1-sqrt_2)^2=(sqrtI-4sqrtI)^2=I`