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AQA Total internal reflection help please??

cladding.PNGPlease correct me if I am wrong but the two rules for total internal reflection to take place is that the light ray must be travelling from a more dense medium to less dense medium. And the angle of incidence must be greater than or equal to the critical angle.......?
(edited 6 years ago)
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Minnie16
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Please explain why these answers are correct?
for part i) If the critical angle is larger and the angle of incidence needs to be equal to or great then the critical angle for TIR, then won't it be hard for the incident angle to increase thus decreasing the chance of light escaping?



(Note: TIR stands for Total Internal Reflection, I shortened it so it's quicker to type)
(edited 6 years ago)
cladding.PNG12.6KB
cladding ms.PNG12.5KB
Original post by Jas1947
cladding.PNGPlease correct me if I am wrong but the two rules for total internal reflection to take place is that the light ray must be travelling from a more dense medium to less dense medium. And the angle of incidence must be greater than or equal to the critical angle.......?

The equation for critical angle is: , where n2 is the cladding and n1 is the core. As n2 increases so does the critical angle because a larger angle is needed to have the same effect (you can check on your calculator by varying the value of n2 whilst keeping n1 constant, you'll see that the angle increases as n2 increases). This means that more light is likely to escape because the angle of refraction also increases so essentially your light is more spread out.

Think of the second one as a car going round a tighter, more curved bend. You are more likely to veer off than on a straight, slightly curved road

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