Question

Interference frings of yellow light of wavelength 6000 A are formed by Billet split lenses. The distance from source to lens is 24 cms. The focal length of lens is 15 cm The lens halves are separated by `0.06` mm. The distance of source to screen is 200 cms. Calculate the fringe width (in mm) Round off the answer to nearest integer.

Answer 1

Correct Answer - `5 mm`
`u=-24`
`v=(uf)/(u+f)`
`v=(-24xx15)/(-24+15)=(124xx15)/8=40`
`Rightarrow D=200-24-40=136` cm
`(R_(1))/(-0.03)=v/u=40/(-24)`
`R_(1)=40/24xx0.03=0.05` mm
`Rightarrow d=0.05xx2+0.06=0.16xx10^(-3)`m
`beta=(lamdaD)/d=(6000xx10^(-10)xx136xx10^(-2))/(0.16xx10^(-3))`
`beta=51xx10^(-4)m=5.1` mm