Question
A beam of light of 
= 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is,
-
1.2 cm
-
1.2 mm
-
2.4 cm
-
2.4 mm
Solution
D.
2.4 mm
From the above figure,
For small
and when 
is counted in rad, tan 
So,
