Question

In Young’s double-slit experiment, the two slits $0.20 \, mm$ apart are illuminated by monochromatic light of wavelength $600 \, nm$ . The screen is $1.0 \, m$ away from the slits. Find the distance of the second bright fringe.

• A. $3 \, mm$
• B. $6mm$
• C. $4mm$
• D. $5mm$

Answer 1

Answer: (B)

Here $d=0.20mm=20\times 10^{- 5}m$
$\lambda =600nm=600\times 10^{- 9}m$
$D=1m$
For the distance of the second bright fringe
$x_{2}=\frac{2 \lambda D}{d}$ $\left[\right.\because x_{n}=\frac{n\lambda D}{d}\left]\right.$
$=\frac{2 \times 600 \times 10^{- 9} \times 1 .0}{20 \times 10^{- 5}}$
$=60\times 10^{- 4}=6\times 10^{- 3}\text{m}=6\text{ mm}$