When a ray of light in a denser medium strikes a rarer medium at an angle of incidence i,the angle of reflection and refraction are respectively r and
r'.if the reflected ray and refracted ray are right angles to each other,what is the critical angle for given pair of media?
A)tan inverse (sin i)
B) cot inverse (tan i )
C)sin inverse (tan r')
D)sin inverse(tan r)