Question

If Young's double slit experiment were submerged in water (n=1.33), how would the inteference pattern change?

Answer 1

On immersing the apparatus in water, the speed of wave travelling in water decreases and hence it’s wavelength decreases as v ? ?

Thus the new wavelength is 1/n times the the original wavelength since n=?1/?2

The fringe width originally is given by ?1=?D/2d

The new fringe width within water will be given by ?2=?D/2nd or ?2=?1/n

Thus the fringe width decreases by a factor of n when immersed in water.

For water, n = 1.33

So:

?2=?1/1.33

That is, the fringe width decreases by a factor of 1.33 when immersed in water.