A) when a ray moves from denser to rarer and incident angle is greater than critical angle
B) when a ray moves from rarer to denser and incident angle is less than critical angle
C) when a ray moves from rarer to denser and incident angle is equal to critical angle
D) none of the above
Correct Answer: A
Solution :
Total internal reflection is the phenomenon of reflection of light into a denser medium from an interface of denser medium and rarer medium. The essential conditions for total internal reflection are : (i) Light should travel from a denser medium to a rarer medium. (ii) Angle of incidence in denser medium should be greater than the critical angle for the pair of media in contact. We may define critical angle for a pair of media in contact as the angle of irecidence to the denser medium corresponding 10 which angle of refraction in the rarer medium is \[{{90}^{o}}\]. It is represented by C and its value depends on the nature of media in contact. Note: In total internal reflection, 100% of incident light is reflected back into the same medium, and there is no loss of intensity. That is why images formed by total internal reflection are much bri-ghter than those formed by mirrors or lenses.
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