Question

A beam of light of wavelength 600 nm from a distance 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 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

Answer 1

The correct option is D 2.4 mm

Distance between the first dark fringes on either side of the centred bright fringe.
$x=\frac{2\lambda D}{d}x=\frac{2\times 600\times {10}^{-9}\times 2}{{10}^{-3}}=24\times {10}^{-4}m$
x = 2.4 mm $(\therefore lm={10}^{3}mm)$