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