Snell's law

If we have two objects with ‘absolute’ refractive indexes of n_1 and n_2, we can say that:

n_1\sin\theta_1=n_2\sin\theta_1

Where:

• n_1 is the refractive index of the first material.
• n_2 is the refractive index of the second material.
• \theta_1 is the angle at which light enters the boundary
• \theta_2 is the angle at which light leaves the boundary

Assuming we know 3 out of the 4 unknowns, we can find any of them. We can re-arrange the formula above into any of:

• n_1=\frac{n_2\sin\theta_2}{\sin\theta_1}
• n_2=\frac{n_1\sin\theta_1}{\sin\theta_2}
• \theta_1=\sin^{-1}(\frac{n_2\sin\theta_2}{n_1})
• \theta_2=\sin^{-1}(\frac{n_1\sin\theta_1}{n_2})

This is Snell’s law!

What is each material?

• The first material is the material the light starts in.
• The second material is the material the light goes into.