The ratio of intensity at the centre of a bright fringe to the intensity at a point distant one-fourth of the distance between two successive bright fringes will be

Options

A. 4
B. 3
C. 2
D. 1

Answer

c

Explanation

Intensity at centre of bright fringe
`l_(0)=l+l+2sqrt(ll*)cos0`
`l_(0)=2l+2l " " [because0^(@)=1]`
Similarly Intensity at point `(P)/(4)`
(with phase difference `=(2pi)/(4)=(pi)/(2))`
`l.=l+l+2sqrt(ll)"cos"(pi)/(2)`
`2l+2sqrt(ll)xx0`
`=2l`
`therefore(l_(0))/(l.)=(4l)/(2l)=2`