Question

In a Young's double slit experiment the spacing between the slits is $0.3mm$ and the screen is kept at a distance of $1.5m$. The second bright fringe is found $6mm$ from the central fringe. The wavelength of the light used in the experiment is

• A. $625nm$
• B. $600nm$
• C. $550nm$
• D. $500nm$

Answer 1

The correct option is B $600nm$

Given:

$D=1.5md=0.3mm\frac{2\lambda D}{d}=6mm$

$\Rightarrow \lambda =\frac{d\times 6}{2D}nm$

$\Rightarrow \lambda =\frac{0.3\times {10}^6\times 6\times {10}^6}{2\times 1.5\times {10}^9}nm$

This gives, $\lambda =600nm$