A parallel beam of monochromatic light of wavelength `5000Å` is incident normally on a single narrow slit of width `0.001mm`. The light is focused by a convex lens on a screen placed on the focal plane. The first minimum will be formed for the angle of diffraction equal to

Options

A. `0^(@)`
B. `15^(@)`
C. `30^(@)`
D. `60^(@)`

Answer

C

Explanation

For 1st minima
`asintheta= lambda`
`implies sintheta= (lambda)/(a)= (5000 xx 10^(-10))/(0.001 xx 10^(-3))`
`implies sintheta= (1)/(2) implies theta= 30^(@)`