In Young’s double-slit experiment the fringe width is $\mathrm{\beta }$. If entire arrangement is placed in a liquid of refractive index n, the fringe width becomes

• A

  $\frac{\mathrm{\beta }}{\mathrm{n}+1}$

• B

  $\mathrm{n\beta }$

• C

  $\frac{\mathrm{\beta }}{\mathrm{n}}$

• D

  $\frac{\mathrm{\beta }}{\mathrm{n}-1}$