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

Options

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

Answer

D

Explanation

Ist minima is formed at a distance `Y=(lambdaD)/a`
where, `lambda` = wavelength of parallel beams
D=focal length a=width of linear aperture
`rArrY=((5xx10^(-5))(0.6))/(0.02xx10^(-2))`
`rArr Y=0.15 cm`