Question

A microwave of wavelength 2.0 cm falls normally on a slit of width 4.0 cm. The angular spread of the central maxima of the diffraction pattern obtained on a screen 1.5 m away from the slit will be:

• A. 60°
• B. 45°
• C. 15°
• D. 30°

Hint:

In diffraction, the first minimum occurs when the path difference equals the wavelength.

Answer 1

The Correct Option is A

{Understanding the diffraction formula} 
The condition for minima in diffraction is: \[ d \sin \theta = n \lambda \] For the first minimum: \[ \sin \theta = \frac{\lambda}{d} = \frac{2}{4} = \frac{1}{2} \] \[ \theta = 30^\circ \] Angular spread: \[ 2\theta = 60^\circ \] Thus, the correct answer is \( 60^\circ \).