Question

In Young's double slit experiment distance between two sources is $0.1 \,mm$. The distance of screen from the source is $20\, cm$. Wavelength of light used is $5460 Å$. Then, angular position of the first dark fringe is

• A. $0.08^{\circ}$
• B. $0.16^{\circ}$
• C. $0.20^{\circ}$
• D. $0.31^{\circ}$

Answer 1

Answer: (B)

Angular position of first dark fringe
$\theta_{1} = \left(2\times1-1\right) \frac{\lambda}{2d} $
$= \frac{\lambda}{2d} = \frac{5460\times 10^{-10} }{2 \times 0.1 \times 10^{-3}} $
$= 2730 \times 10^{-6} rad $
$ = 2730 \times 10^{-6} \times \frac{180}{\pi}$
$ = 0.16^{\circ}$