A fringe width of 6 mm was produced for two slits separated by
Question:

A fringe width of $6 \mathrm{~mm}$ was produced for two slits separated by $1 \mathrm{~mm}$ apart. The screen is placed $10 \mathrm{~m}$ away. The wavelength of light used is ‘ $\mathrm{x}$ ‘ $\mathrm{nm}$. The value of ‘ $\mathrm{x}$ ‘ to the nearest integer is______

Solution:

$(600)$

$\beta=\frac{\lambda D}{d}$

$\lambda=\frac{\beta d}{D}$

$\lambda=\frac{6 \times 10^{-3} \times 10^{-3}}{10}$

$\lambda=6 \times 10^{-7} \mathrm{~m}=600 \times 10^{-9} \mathrm{~m}$

$\lambda=600 \mathrm{~nm}$