Question

Two slits 0.1 mm apart are arranged 1.20 m from a screen. Light of wavelength 600 nm from a distant source is incident on the slits.
Find the angular width (in degrees) of the first bright fringe.

Hint:

Angular width is independent of the screen distance but depends on the wavelength and slit separation.

Answer 1

The angular width is given by: \[ \theta = \frac{\lambda}{d} \] Substituting values: \[ \theta = \frac{600 \times 10^{-9}}{1.0 \times 10^{-4}} \] \[ \theta = 6.0 \times 10^{-3} \text{ rad} \] Converting to degrees: \[ \theta = 6.0 \times 10^{-3} \times \frac{180}{\pi} \] \[ \theta \approx 0.034^\circ \] Thus, the angular width is 0.034°.