When an unpolarised ray of light falls at the air-glass interface at an angle of incidence ${60}^o$, it is observed that the angle between the reflected ray and the refracted ray is ${90}^o$. Then the refractive index of glass is $(\sqrt{3}=1.732)$

• A

  1.5

• B

  1.732

• C

  1.333

• D

  1.61