Question

A slit of width $d$ is placed in front of a lens of focal length $0.5m$ and is illuminated normally with light of wavelength $5.89\times {10}^{-7}m$. The first diffraction minima on either side of the central diffraction maximum are separated by $2\times {10}^{-3}m$. The width $d$ of the slit is _______ $m$.

Answer 1

Given that width of central maxima
$=2\times {10}^{-3}m$
$\therefore \frac{2\lambda D}{d}=2\times {10}^{-3}$
$\Rightarrow d=\frac{2\times 5.89\times {10}^{-7}\times 0.5}{2\times {10}^{-3}}=2.945\times {10}^{4}m$.