Question

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

• A. $3mm$
• 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
$x_2=\frac{2\lambda D}{d}$ $[\because x_n=\frac{n\lambda D}{d}]$
$=\frac{2\times 600\times 10^{-9}\times 1.0}{20\times 10^{-5}}$
$=60\times 10^{-4}=6\times 10^{-3}\text{m}=6\text{ mm}$