Light rays from a source are incident on a glass prism of index of refraction $\mathrm{\mu }$ and angle of prism $\mathrm{\alpha }$. At near normal incidence, the angle of deviation of the emerging rays is

• A

  $(\mathrm{\mu }-2)\mathrm{\alpha }$

• B

  $(\mathrm{\mu }-1)\mathrm{\alpha }$

• C

  $(\mathrm{\mu }+1)\mathrm{\alpha }$

• D

  $(\mathrm{\mu }+2)\mathrm{\alpha }$