Exam-style question
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What condition must be met for total internal reflection to occur in optical fibres?.
- A.The angle of incidence must be greater than the critical angle.
- B.The angle of incidence must be less than the critical angle.
- C.The refractive index of the second medium must be greater than the first.
- D.The light must travel through a vacuum.
Model answer
What a good answer should say
- The angle of incidence must be greater than the critical angle.
Explanation
Why this works
Total internal reflection occurs when the angle of incidence exceeds the critical angle, which is determined by the refractive indices of the two media. This principle is essential for the functioning of optical fibres.
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