Refraction of light
Refraction is the bending of light that occurs when it crosses a boundary between materials of different optical density (Refractive Index).
The angle of bending can be calculated using a simple formula known as the Snell's law:
n1sinθ1=n2sinθ2 with n being the refractive indices of the materials, and theta the angle of incidence/refraction of incoming light.
Under certain conditions refraction can be extreme and the light does not cross the boundary, but is reflected backwards: this is Total Internal Reflection.
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Figure description: Schematic representation of the refraction of light as it travels from a medium with a low refractive index (air) to a medium with a higher refractive index (water).
