Question

What change is observed when the whole pattern is immersed in water?

(a) Fringe width decreases

(b) Fringe width increases

(c) Colored fringes

(d) The bright and dark fringes will change position

I had been asked this question in examination.

Question is taken from Young’s Experiment in division Interference of Engineering Physics II

Answer 1

Right answer is (a) Fringe width decreases

For explanation I would say: When the whole apparatus of Young’s Double slit experiment is immersed in water, the only change is the pattern shrinks a bit. The width of the fringes decreases, as an external path difference is present because of the water.