Total internal reflection
Total internal reflection can occur when light travels:
Answer B: explanation for every choice
A
Light moving into a higher index bends toward the normal and always refracts.
B
Correct. Total internal reflection requires moving from a higher to a lower index of refraction at an angle beyond the critical angle, as in fiber optics.
C
Below the critical angle, some light refracts out.
D
With equal indices, light passes straight through without bending.
TakeawayTotal internal reflection: high n to low n, beyond the critical angle.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID cp29.