How Do I Calculate the Index of Refraction in a Prism?

[mikeyplus10]

Homework Statement

For my lab I beamed a laser through an equilateral triangular prism. The angle of incidence was 13 degrees. The light left the prism at an angle 15 degrees to the normal. How would I calculate the index of refraction of the prism? (air = 1)

Homework Equations

The equation I need to use is θ_c = sin^-1 (n2/n1)
Snell's law

The Attempt at a Solution

I have tried using snell's law to find the first refraction in the prism. 1.00*(sin13) = n_2*θ_2. I believe to find θ_2, I need to use the geometry of the triangle, but am not sure where to begin

 

[tiny-tim]

welcome to pf!

hi mikeyplus10! welcome to pf!

(try using the X² and X₂ buttons just above the Reply box

first, draw a diagram, including the normals

(and remember that the angle between two lines is the same as the angle between their normals)