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 the centre of bright fringe,
`I_(0)=I+I+2sqrt(II) cos 0^(@)=2I+2I=4I`
Intensity at a point distant `(beta)/(4)`
(with a phase difference`=(2pi)/(4)=(pi)/(2)`) is
`I'=I+I+sqrt(II)"cos"(pi)/(2)=2I " "[because "cos"(pi)/(2)=0]`
`therefore (I_(0))/(I')=(4I)/(2I)=2`