A parallel beam of monochromatic light of wavelength 489 nm passes through a single slit of width 0.3 mm. The angular width of the central maxima is

$3.26 × 10^{-3}\, rad$

The correct answer is Option (4) → $3.26 × 10^{-3}\, rad$

Given:

• Wavelength, $\lambda = 489 \, \text{nm} = 489 \times 10^{-9} \, \text{m}$
• Slit width, $a = 0.3 \, \text{mm} = 0.3 \times 10^{-3} \, \text{m}$

Angular width of central maximum is given by:

$\theta = \frac{2\lambda}{a}$

Substitute values:

$\theta = \frac{2 \times 489 \times 10^{-9}}{0.3 \times 10^{-3}}$

$\theta = \frac{978 \times 10^{-9}}{0.3 \times 10^{-3}}$

$\theta = 3.26 \times 10^{-3} \, \text{radians}$

So, angular width ≈ 0.00326 radians