Refraction

[dsafla]

If

Sin(theta r)/Sin(theta i) is reversed from Sin(theta i)/Sin(theta r) = n, what does this mean? I'm quite confused since I'm doing a physics lab, and the class was told to make a graph where we measured angles with polar paper, pins and plexyglass. Could it possibly the index of refraction of air?

Thanks so much.

[Doc Al]

That n is the index of refraction of the plexyglass. Here's the explanation. First, Snell's law of refraction is this:
n_1 sin\theta_1 = n_2 sin\theta_2
Where 1 and 2 represent the two different media. If you are going from air (1) to plexyglass (2), then you can rewrite this as:
sin\theta_i = n_2 sin\theta_r
(Note that the index of refraction of air is n = 1.)
So... you can solve for the index of refraction of the plexyglass:
n_2 = \frac{sin\theta_i}{sin\theta_r}