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Total internal reflection (TIR) occurs when:
ALight travels from a rarer medium to a denser medium at any angle
BLight travels from a denser medium to a rarer medium AND the angle of incidence exceeds the critical angle
CTwo media have the same refractive index
DLight strikes the surface perpendicularly
Answer & Solution
Correct answer: B. Light travels from a denser medium to a rarer medium AND the angle of incidence exceeds the critical angle
**TIR conditions**: (i) **light travels from denser to rarer medium**, (ii) **angle of incidence > critical angle i_c**. Beyond i_c no refraction is possible — light is **completely reflected back** with no transmission loss.
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