GK QUESTION#2926
Total internal reflection happens when light moves from:
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Answer
D. A denser medium to a rarer medium at an angle of incidence greater than the critical angle.
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Explanation
Total internal reflection requires travel from a higher refractive index to a lower one, with incidence greater than the critical angle. At the critical angle, the refracted ray is at 90° to the normal; total internal reflection occurs above it. Real optical fibres still have losses.