Newtonian Particle Theory of Light
Light refraction is a common phenomenon that is readily observed with the naked eye. Yet a mathematical formula to describe the effect was only realized in the early 17thcentury.
In terms of the modern-day quantity refractive index n, Snell’s result is:
n1 sinΘ1= n2 sinΘ2,
where Θ1and Θ2, are the respective angles of incidence and refraction as light passes from one medium to another.