Figure shows two light rays that are initially exactly in phase and that reflect from several glass surfaces. Neglect the slight slant in the path of the light in the second arrangement. The path length difference in terms of wavelength `lamda` is :

Options

A. 2d
B. `(d+lamda)`
C. `(2d+lamda)`
D. none of these

Answer

C

Explanation

`x_(1)=5d+4xxlamda//2=5d+2lamda`
and `x_(2)=3d+2xxlamda/2=3d+lamda`
`therefore" "Deltax=x_(1)~x_(2)=(5d+2lamda)-(3d+lamda)=(2d+lamda)`.