Question

In Young’s double-slit experiment if the distance between two slits is halved and distance between the slits and the screen is doubled, then what will be the effect on fringe width?

(a) Doubled

(b) Decreases four times

(c) Increases four times

(d) Halved

This question was posed to me by my college director while I was bunking the class.

The query is from Wave Optics topic in portion Wave Optics of Physics – Class 12

Answer 1

The correct choice is (c) Increases four times

The explanation: Original fringe width is given as ➔ β = \(\frac {D\lambda }{d}\).

So, the new fringe width is ➔ β’ = \(\frac {\lambda.2D}{ ( \frac {d}{2} ) }\)

β’ = 4β

Therefore, the new fringe width is 4 β.