In Young's double slit experiment, if `I_(0)` is intensity of light from each sources, what is the intensity at a point on screen where two waves arrive having a phase diff. of `60^(@)` and `120^(@)`.

Answer

`3 I_(0), I_(0)`

Explanation

At any point on the screen, `I = 4 I_(0) cos^(2) phi//2`
When `phi = 60^(@)`,
`I = 4 I_(0)(cos 60^(@)//2)^(2) = 4 I_(0) (sqrt(3)//2)^(2) = 3 I_(0)`
When `phi = 120^(@), I = 4 I_(0) (cos 120^(@)//2)^(2) = I_(0)`