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# Refraction question help watch

1. Hey guys I've been stuck on this one question for a while now and I have a test on this topic next week, unfortunately I can't contact my teacher because half term and so have come here for help. It's a multiple choice question in my physics textbook (AQA Physics 1 by Hodder) and it's about refractive index, Snell's Law and total internal reflection. So the question is:

A prism for which all angles are 60 degrees has a refractive index of 1.5. What angle of incidence at the first face will just allow total internal reflection at the second face?

A) 48 degrees B) 42 degrees
C) 28 degrees D) 60 degrees

Please all help is appreciated, if anyone knows how to do this it would be nice if you explain as well.
2. You need to work out the incident angle at the air/glass boundary if the angle of incidence at the glass/air boundary is the critical angle, which leads you to a diagram like this;

I'm assuming you can work out the critical angle. That makes it easy to work out the angle of refraction at the air/glass boundary, from which you can work out the angle of incidence.
3. By the way, my diagram is seriously not to scale! I do get one of those answers.
4. I'm also stuck on this question, can you go through it step by step please because I dont seem to understand the diagram
I'm also stuck on this question, can you go through it step by step please because I dont seem to understand the diagram
I hope the following steps are clear for you to follow.

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Updated: December 29, 2016
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