Physics - Wave Optics Question with Solution | TestHub

Given:
Slit width, $a=0.3\text{ mm}=3\times 10^{-4}\text{ m}$
Distance of screen, $D=1.5\text{ m}$
Wavelength, $\lambda =4500\text{ A˚}=4.5\times 10^{-7}\text{ m}$

The distance between the first minimum on either side of the central maximum is the linear width of the central maximum.

Width of central maximum, $W=\frac{2\lambda D}{a}$

Substituting the given values:
$W=\frac{2\times 4.5\times 10^{-7}\times 1.5}{3\times 10^{-4}}$

$W=\frac{13.5\times 10^{-7}}{3\times 10^{-4}}$

$W=4.5\times 10^{-3}\text{ m}$

$W=4.5\text{ mm}$

Answer: 4.5 mm