# Homework Help: Geometrical optics #3

1. Apr 12, 2014

### h20proof

In the following diagram find the distance d if a=4.0 mm, Θ=30°

n_asinΘ_a=n_bsinΘ_b: snells law
a^2+b^2=c^2: pythagorean theorem

I think I got the angle to the problem correct. I am not sure if this is correct. Is this correct Θ_b=sin^-1(1sin30/1.52)?

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2. Apr 12, 2014

### Staff: Mentor

That will give you the internal angle.

You are apparently required to find the offset distance, d, of the emergent ray.

3. Apr 12, 2014

### h20proof

thank you. How do you find it?

4. Apr 13, 2014

### Staff: Mentor

Using geometry. Specifically, the geometry of right-angled triangles.

You start by drawing a large clear diagram, and using a straight-edge to make all your straight lines look straight. Any lines you draw can be made into a side of a right-angled triangle.

5. Apr 13, 2014

### h20proof

okay, I still don't see it.

6. Apr 13, 2014