Two sources of light having intensities `I_(1) and 4I_(1)` emit the light waves. The phase difference between the light waves interfering at a point is `90^(@)` . The intenity 'I' of light at that point, is

Options

A. `I= 2I_(1)`
B. `I= 3I_(1)`
C. `I= 4I_(1)`
D. `I= 5I_(1)`

Answer

D

Explanation

`I= I_(2)+I_(2)+sqrt(I_(1)I_(2)) 2 cos (alpha_(1)-alpha_(2))`
`=I_(4)+4I_(1)+sqrt(I_(1)4I_(1)) 2 cos 90`
`=5I_(1)`