A linear aperture whose width is 0.02 cm is placed
immediately in front of a lens of focal length 60 cm.
The aperture is illuminated normally by a parallel
beam of wavelength 5 X ``10^{-5}`` cm. The distance of
the first dark band of the diffraction pattern from
the centre of the screen is :-
(1) 0.20 cm
(2) 0.15 cm
(3) 0.10 cm
(4) 0.25 cm