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. 3I and I
D. 9I and I

Answer

D

Explanation

`I_(max)=I_(1)+I_(2)+2sqrt(I_(1)I_(2))`
`=I+4I+2sqrt(Ixx4I)`
`=5I+2xx2I`
`=5I+4I=9I`
`I_("min")=I+4I-2sqrt(Ixx4I)`
`=5I-4I=I`