A linear aperture whose width is `0.02cm` is placed immediately in front of a lens of focal length `60cm`. The aperture is illuminated normally by a parallel beam of wavelength `5xx10^-5cm`. The distance of the first dark band of the diffraction pattern from the centre of the screen is

Options

A. `0.10cm`
B. `0.25cm`
C. `0.20cm`
D. `0.15cm`

Answer

D

Explanation

Here, `a=0.02cm=2xx10^(-4)m, D=60cm=0.6m lambda=5xx10^(-5)cm=5xx10^(-7)m`
Position of first minima on the diffraction pattern,
`y_(1)=(Dlambda)/(a)=(0.6xx5xx10^(-7))/(2xx10^(-4))=0.15cm`