Fringe width in water

Question

In a double slit experiment, if the fringe width is !!beta!! in air. If the same experiment is carried out in water the fringe width will be:

  • !!beta/mu!!
  • !!betamu!!
  • !!beta!!

Solution

When the same experiment is conducted in water the only change compared to in air would be in the wavelength of light.

!!lambda_(water)=lambda_(air)/mu!!

The dark and bright spots are formed due to the interference of light. If we change the wavelength the fringe width will change.

fringe width!!=(lambdaD)/d!!

fringw width in water !!=(lambda_(water)D)/d!!

!!=(lambda_(air)/mu D)/d!!

!!=1/mu (lambda_(air) D)/d!!

!!=beta/mu!!

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