Why does an optical fibre need a cladding with a lower refractive index than the core?
Answer and explanation
Correct answer: D. So that light travelling at more than the critical angle is totally internally reflected
- Step 1: Total internal reflection occurs when light goes from a higher to a lower refractive index and meets the boundary above the critical angle. Answer: So that light travelling at more than the critical angle is totally internally reflected. Why not the others: refracting out would lose the signal; speed is not the aim; absorption would reduce the signal.
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