In Young's double-slit experiment , we get 60 fringes in the field of view if we use light of wavelength `4000 Å`. The number of fringes we will get in the same field of view if we use light of wavelength `6000 Å` is

Options

A. 40
B. 90
C. 60
D. 50

Answer

A

Explanation

`x_(n)=(D)/(d) n_(1) lambda_(1)=(D)/(d) n_(2) lambda_(2)`
`:.n_(2)=(lambda_(1))/( lambda_(2))n_(1)`
`:.n_(2)=(4000xx60)/(6000)=40`