In a Young's double slit experiment, the fringe width is found to be `0.4mm`. If the whole apparatus is immersed in water of refractive index `4//3` without disturbing the geometrical arrangement, the new fringe width will be

Options

A. `0.30 mm`
B. `0.40 mm`
C. `0.53 mm`
D. `0.20 mm`

Answer

A

Explanation

`mu=(beta_("air"))/(beta_("den"))`
`:. beta_("den") =(beta_("air"))/(mu)=(0.4)/(4//3)=0.3 mm`