Two point monochromatic and coherent sources of light of wavelength`I`are placed on the dotted line in front of an large screen.The souces emti waves in phase with each other.the distance between`S_(1)&S_(2)`is `'d'`while theiri distance from the screen is much larger ,then,

"`rarr`if `d=7lambda//2,O` will be a minima
`"rarr`if `d=4.3lambda,O` there will be a total of 8minima on y axis
`"rarr`if `d=7lambda,O` will be a minima
`"rarr`if `d=lambda ` there will be only maxima on the screen.

Options

A. `1,2&3`
B. `2,3&4`
C. `1,2,3&4`
D. `1,3,&4`

Answer

C

Explanation

since path difference at `O` is(2n-1)`lambda//2`so,O is a minima (2) as we move up or down on the screen path different becomes `7lambda//2,5lambda//2,3lambda//2,lambda//2` on both side so no of minima is`8`.
(3) Since path differnce at `O` is `nlambda`,So`O` is maxima
As we move up or down on the screen phase different of point alwasys remain less than`lambda1` so there is only central maxima.