Solving index of refraction for Total Internal Reflection

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The discussion focuses on solving for the index of refraction in the context of total internal reflection using Snell's Law. Participants clarify that the critical angle must be equal to or greater than the angle of incidence for internal reflection to occur. There is confusion regarding the relationship between angles at different interfaces, specifically the angle of incidence and the angle of refraction. The importance of expressing angles in terms of known variables is emphasized to solve the problem correctly. Overall, the thread highlights the complexities involved in applying Snell's Law to total internal reflection scenarios.
RaulTheUCSCSlug
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Homework Statement


Screenshot 2015-03-18 at 7.00.08 PM.png


Homework Equations


Snell's Law
n1sin(theta_1)=n2sin(theta_2)
Total Internal Refraction:
sin(theta_c)=(n_2/n_1)

lambda_n=lambda_n

The Attempt at a Solution



So I drew the triangle and this is what I got, and well here is just a picture so far of what I have.
impossibleprobleeem.jpg

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I've done this problem before and got n=(theta)-(arcsin((sin(theta)/n)) and from there I have no idea. But I did a different approach. Any ideas. I've tried differentiating implicitly after that and trying to integrate and just got a huge mess.
 
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Show your work in readable form.
 
ehild said:
Show your work in readable form.
I just wrote down what I know and some equations, I found out the angle of refraction when the laser beam first enters. But I don't know what to do after.
 
Find the angle of incidence at S2.
 
It would be 90 degrees minus the angle of refraction. But doesn't it have to equal the angle at which it internally reflects?
 
RaulTheUCSCSlug said:
It would be 90 degrees minus the angle of refraction. But doesn't it have to equal the angle at which it internally reflects?
Yes, it should be equal or greater than the critical angle, at which internal reflection occurs. But it is not 90°minus the angle of refraction at S1. Give it in terms of theta and the angle of refraction.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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