Question

A white light is passed through the two narrow slits and produced a pattern of alternating bright and dark lines on the screen as shown above. What will effects on the central bright band , if the distance between screen and slits are increased?

• A. become wider
• B. become narrower
• C. remain unchanged
• D. disappear completely
• E. rotate ${90}^{\circ }$

Answer 1

The correct option is A become wider

The setup shown is that of Young's Double Slit Experiment.

The fringe width in the experiment is given as $\beta =\frac{D\lambda }{d}$

where $d$ is the distance between the slits, $D$ is the distance between screen and slits.

Hence the central fringe also widens when distance between screen and slits increases.