$A$ ray of light passes from a denser medium to a rarer medium at an angle of incidence $i$. The reflected and refracted rays make an angle of $90^{\circ}$ with each other. The angles of reflection and refraction are respectively $r$ and $r^{\prime}$. The critical angle is given by:

  • A
    $\sin ^{-1}(\tan r)$
  • B
    $\sin ^{-1}(\tan r^{\prime})$
  • C
    $\sin ^{-1}(\cot r)$
  • D
    $\tan ^{-1}(\sin i)$

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