optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultra ...

, an Abbe prism, named for its inventor, the German physicist

Ernst Abbe Ernst Karl Abbe HonFRMS (23 January 1840 – 14 January 1905) was a German physicist, optical scientist, entrepreneur, and social reformer. Together with Otto Schott and Carl Zeiss, he developed numerous optical instruments. He was also a ...

, is a type of ''constant deviation dispersive prism'' similar to a Pellin–Broca prism.

Structure

The prism consists of a block of glass forming a right prism with 30°–60°–90° triangular faces. When in use, a beam of light enters face AB, is refracted and undergoes

total internal reflection Total internal reflection (TIR) is the optical phenomenon in which waves arriving at the interface (boundary) from one medium to another (e.g., from water to air) are not refracted into the second ("external") medium, but completely reflecte ...

from face BC, and is refracted again on exiting face AC. The prism is designed such that one particular

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...

of the light exits the prism at a deviation angle (relative to the light's original path) of exactly 60°. This is the minimum possible deviation of the prism, all other wavelengths being deviated by greater angles. By rotating the prism (in the plane of the diagram) around any point O on the face AB, the wavelength which is deviated by 60° can be selected. The dispersive Abbe prism should not be confused with the non-dispersive Porro–Abbe or Abbe–Koenig prisms.

References

* {{cite book , author=Hecht, Eugene , title=Optics (4th ed.) , publisher=Pearson Education , year=2001 , isbn=0-8053-8566-5 Prisms (optics) German inventions