Question

A beam of light of wavelength 600 nm from a distant source falls on a single slit I 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. 2.4cm
• D. 2.4mm

Answer 1

The Correct Option is D

$ \beta =\frac{\lambda D}{d}=\frac{600\times {{10}^{-9}}\times 2}{1\times {{10}^{-3}}}=12\times {{10}^{-4}}\,m $ So, distance between the first dark fringes on either side of the central bright fringe $ X=2\beta $ $ =2\times 12\times {{10}^{-4}}m $ $ =24\times {{10}^{-4}}m $ $ =2.4\,mm $