Snell's Law, also known as the Law of Refraction, is a formula describing the relationship between the angles of incidence and refraction when light (or other electromagnetic radiation) passes between two media:
θk is the angle measured from the normal (the line perpendicular to the surface)
vk is the velocity of light in each medium (m/s)
nk is the refractive index in each medium (no unit)
λk is the wavelength of the light in each medium (m)
Total Internal Reflection
Snell's Law is valid only as long as sinθ1 is no greater than n2n1. When n2< n1, i.e. light travels from a medium of a higher index of refraction to one with a lower refractive index, the angle θc defined by
θc = sin−1n2n1
is called the critical angle. This angle is the largest possible incident angle which will create a refracted ray. As the incident angle θ1 increases towards θc, the proportion of the light refracted through the surface decreases and the proportion reflected increases. When θ1≥θc, all light is reflected, a situation known as Total Internal Reflection.
Click on the graph or slide the slider to change the angle of incidence.
Angle of incidence =
A list of refractive indices
Index of refraction
Heavy Flint Glass
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