Chapter 35 Light: Reflection and Refraction
... At some critical angle of incidence, θc, the light is totally reflected back into the medium of higher refractive index. This is called the total internal reflection and was first noted by Kepler in 1604. ...
... At some critical angle of incidence, θc, the light is totally reflected back into the medium of higher refractive index. This is called the total internal reflection and was first noted by Kepler in 1604. ...
Retroreflector
A retroreflector (sometimes called a retroflector or cataphote) is a device or surface that reflects light back to its source with a minimum of scattering. In a retroreflector an electromagnetic wavefront is reflected back along a vector that is parallel to but opposite in direction from the wave's source. The angle of incidence at which the device or surface reflects light in this way is greater than zero, unlike a planar mirror, which does this only if the mirror is exactly perpendicular to the wave front, having a zero angle of incidence.