Light of wavelength `lambda = 5890 Å` fall on a double-slit arrangement having separation `d = 0.2 mm`. A thin lens of focal length `f = 1 m` is placed near the slits. The linear separation of fringes on a screen placed in the focal plane of the lens is

Options

A. 3 mm
B. 4 mm
C. 2 mm
D. 1 mm

Answer

a.

Explanation

`beta = (Delta lambda)/(d) = (f lambda)/(d) = (1 xx 4890 xx 10^(-10))/(0.2 xx 10^(-3))`
`= 0.29 xx 10^(-2) m = 2.9 mm ~~ 3 mm`