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 × 10–5 cm. The distance of the first dark band of the diffraction pattern from the centre of the screen is
0.15 cm
0.10 cm
0.25 cm
0.20 cm
Explanation:
Position of 1st minima
$y = \dfrac{\lambda D}{a} = \dfrac{(5 × 10^{–8})(0.6)}{0.02 × 10^{–2}}$ = 0.15 cm.