What is the Relationship Between Snell's Law and the Index of Refraction?

[Peter G.]

Hi,

I am learning about refraction and the million ways in which Snell's Law is presented to me is making me confused...

So, I understand that:

sin i / sin r, will give me the ratio of speeds c_i/c_r and λ_i/λ_r

However, I can't understand this form of:

n₁sin i = n₂ sin r

How does it drop out?

Thanks,
Peter G.

 

[Doc Al]

Don't forget the meaning of the index of refraction:
n = c/v (where c = speed of light in a vacuum and v = speed of light in the media)

In your notation:
c₁ = c/n₁
c₂ = c/n₂