Question Detail
Question
What condition must be met for total internal reflection to occur, as defined by the critical angle?
Correct Answer
Option C is the correct answer.
Detailed Explanation
Page 47 introduces the critical angle: 'If light passes into a medium with a smaller index of refraction, the angle of refraction is larger. There is an angle of incidence for which the angle of refraction will be 90°; this is called the critical angle.' Page 48 then states, 'If the angle of incidence is larger than this, no transmission occurs. This is called total internal reflection.' Combining these, it means light goes from higher to lower 'n', and the incidence angle exceeds the critical angle.
Hint
Total internal reflection happens when light tries to escape a denser medium into a less dense one at a shallow enough angle.