Q. A beam of light of wavelength 600 nm from a distance source falls on a single slit 1.00 mm wide and the resulting diffraction pattern is observed on a screen 2m away. The distance between the first dark fringes on either side of the central bright fringe is
A) 1.2 cm
B) 1.2 mm
C) 2.4 cm
D) 2.4 mm
Explanation
(d) $\lambda = 600\ nm = 6 \times 10^{- 7}m$
$a = 1\ mm = 10^{- 3}m,D = 2\ m$
Distance between the first dark fringes on either side of central bright fringe=width of central maximum
$= \frac{2\lambda D}{a} = \frac{2 \times 6 \times 10^{- 7} \times 2}{10^{- 3}}$
$= 24 \times 10^{- 4}m = 2.4\ mm$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.