In a Young’s double slit experiment; the slits are illuminated by a monochromatic light. The entire set up is immersed in pure water. In order to restore the original fringe width, what can be done? Choose the incorrect statement.

When the YDSE set up is immersed in liquid, the fringe width decreases due to decrease in λ  when compared with that in air. β=λDd . β  Can be increased i.e., the initial value can be restored by following the options(A),(B),(C) . Due to introduction of thin transparent slab, only shift of interference pattern takes place but there will be no change in fringe width. Hence ‘D’ is wrong statement i.e. correct answer.