Question

A beam of light of wavelength $600 \, nm$ from a distant 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 central bright fringe is

• A. $1.2 \, cm$
• B. $1.2 \, mm$
• C. $2.4 \, cm$
• D. $2.4 \, mm$

Answer 1

Answer: (D)

The distance between the first dark fringes on either side of central bright fringe is
$\Rightarrow 2y=\frac{2 D \lambda }{a}$
$\Rightarrow 2y=\frac{2 \times 2 \times 6 \times 1 0^{- 7}}{1 \times 1 0^{- 3}}$
$\Rightarrow 2y=24\times 10^{- 4} \, m$
$\Rightarrow 2y=2.4 \, mm$