Optical Fibres
2 marks · EasyThe table shows the refractive indices for different parts of an optical fibre:
| Part of fibre | Refractive index |
|---|---|
| Core | 1.52 |
| Cladding | 1.48 |
State which part ensures total internal reflection occurs, and explain your answer.
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Core; because it has the higher refractive index so light going from core to cladding can be totally internally reflected.
Must show: Core identified, Explanation about higher refractive index
Common mistakes: Swapping core and cladding roles
Show mark scheme and worked solution
Marking points
B1 · 1 mark · Correctly identifies 'core'
B2 · 1 mark · Explains core has higher refractive index, enabling TIR
Worked solution
The core (refractive index 1.52) enables total internal reflection because it is higher than the cladding (1.48), so light travelling from core to cladding at a high enough angle is totally internally reflected.