A ray of light is incident at an angle i from denser to rare medium. The reflected and the refracted rays are mutually perpendicular. The angle of reflection and the angle of refraction are respectively r and r' , then the critical angle will be [IIT-JEE 1983; MP PET 1995; CBSE PMT 1996; MP PMT 1985, 99; Pb. PET 2002]

• A. \[{{\sin }^{-1}}(\sin \,r)\]
• B. \[{{\sin }^{-1}}\,(\tan r')\]
• C. \[{{\sin }^{-1}}\,(\tan i)\]
• D. \[{{\tan }^{-1}}(\sin i)\]