A beam of light of wavelength 600 nm from a distant source
falls on a single slit 1.0 mm wide and the resulting diffraction pattern is
observed on a screen 2m away. What is the distance between the first dark
fringe on either side of the central bright fringe?

Options

A. `1.2 cm`
B. `1.2 mm`
C. `2.4 cm`
D. `2.4 mm`

Answer

D

Explanation

Here, `lambda = 600 nm = 6 xx 10^(-7)m`
`a = 1 mm = 10^(-3)m, D = 2 m`.
Distance between first dark fringes on either side of central bright fringe is width of central
maximum, which is `= (2lambda D)/(a) = (2 xx 6 xx 10^(-7) xx 2)/(10^(-3))`
`= 2.4 xx 10^(-3)m = 2.4 mm`