A parallel beam of light `(lambda= 5000 Å)` is incident at an angle `theta=30^@` with the normal to the slit plane in a Young's double slit experiment. The intensity due to each slit is `I_0`. Point O is equidistant from `S_1 and S_2`. The distance between slits is 1mm.

Options

A. the intensity at O is `2I_(0)`
B. the intensity at O is zero
C. the intensity at a point on the screen 4m from O is `4I_(0)`
D. the intensity at a point on the screen 4m from O is zero

Answer

C

Explanation

Path difference at point O is ` d sin alpha=0.5 mm ` corresponding phase difference `Deltaphi=(2pi)/(lambda) xx Delta phi`
`=(2pi(0.5xx10^(-3)))/(5000xx10^(-10))=2000 pi =2pixx1000`
`rArr` O is point corresponding -10 maxima.
the point at 1m below O corresponding to central maxma.