Question

A beam of light of wavelength $600nm$ from a source falls on a single slit $1mm$ 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. $2.4cm$
• B. $2.4mm$
• C. $1.2mm$
• D. $1.2cm$

Answer 1

Answer: (B)

$2.4mm$

Distance between central axis and the first dark fringe on any side $=\beta =\frac{D\lambda }{d}=\frac{2\times 600\times {10}^{-9}}{{10}^{-3}}$

$=1.2mm$

Thus total distance between the dark fringes on either side = $2\times 1.2mm=2.4mm$