Optical Fibres
1 mark · EasyWhat property must the core of an optical fibre have compared to the cladding to allow total internal reflection?
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Correct option: The core must have a higher refractive index than the cladding.
Common mistakes: Choosing 'lower refractive index'
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Marking points
B1 · 1 mark · Correct option selected: core has higher refractive index than cladding.
Worked solution
Total internal reflection happens when light travels from a region of higher to lower refractive index. So, the core must have a higher refractive index.