Question

If the separation between the two slits is decreased in Young’s double-slit experiment keeping the screen position fixed, what will happen to the width of the fringe?

(a) Decreases

(b) Increases

(c) Remains the same

(d) Independent

The question was posed to me in an interview for job.

My question is based upon Wave Optics in section Wave Optics of Physics – Class 12

Answer 1

The correct choice is (b) Increases

To explain I would say: Fringe width is expressed as:

β = \(\frac {D\lambda }{d}\).

So, as the separation (d) between the two slits decreases, the fringe width increases. They are inversely proportional to each other.