# Where should a second hole be placed in order for the light [ ]?

1. Aug 24, 2013

### s3a

"Where should a second hole be placed in order for the light [...]?"

1. The problem statement, all variables and given/known data
The problem and the solution are attached as jpg files. (Given that the problem depends on the drawing, I think it's more convenient for the reader to view the text in the image as well.)

2. Relevant equations
Snell's Law: $n_1 sin θ_1 = n_2 sin θ_2$

3. The attempt at a solution
In the TheSolution.jpg, I don't, mathematically, get how it can it say $2.54 sin 48.6° = 1.0 sin θ_2$ since that would mean that $asin(2.54 sin(48.6°))$ would not exist (but, I do get total internal reflection when thinking about it theoretically rather than mathematically).

Also, how is the leftmost 11.4° angle (from the normal) found to be 11.4°?

Any input would be greatly appreciated!

#### Attached Files:

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• ###### TheSolution.jpg
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26.2 KB
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2. Aug 24, 2013

### Staff: Mentor

The point is that the refraction ray cannot exist--thus you have total internal reflection. (Review how you'd determine the critical angle for total internal reflection.)

Consider the triangle formed at the lower left of the prism, with one angle given as 60°.

3. Aug 25, 2013

### s3a

Thanks, I now get it! :)