In the standard Young's double slit experiment, the intensity on the screen at a point distant `1.25` fringe widths from the central maximum is (assuming slits to be identical)

Options

A. `1/2 I_(max)`
B. `1/4 I_(max)`
C. `1/3 I_(max)`
D. `I_(max)`

Answer

A

Explanation

Path difference `Deltax =(yd)/D=((1.25lambdaD)/d)(d/D)`
`=1.25lambda=5/4lambda`
Phase difference `phi=(2pi)/lambda.Deltax`
`=(2pi)/lambdaxx5/4lambda=5/2pi`
`:. phi/2=5/4pi=225^(@)`
`:.` Intensity `I=I_(max)"cos"^(2)phi/2=1/2I_(max)`