Aparallel beam of monochromatic light of wavelength `4000 Å` is incident normally on a single narrow slit of width 0.0008 mm. The light is focused by a a convex lens on a screen placed in focal plane. The first minimum will be formed for the angle of diffraction equal to

Options

A. `0^(@)`
B. `15^(@)`
C. `30^(@)`
D. `50^(@)`

Answer

C

Explanation

For first minima
`d sin theta= n lambda=1 lambda [ :. N=1]`
`sin theta=(lambda)/(d)`
`=(5000xx10^(-10))/(0.001xx10^(-3))=0.5`
`:. theta=30^(@)`