A Pellin–Broca prism is a type of constant-deviation dispersive

prism Prism usually refers to: * Prism (optics), a transparent optical component with flat surfaces that refract light * Prism (geometry), a kind of polyhedron Prism may also refer to: Science and mathematics * Prism (geology), a type of sedimentary ...

similar to an

Abbe prism In optics, an Abbe prism, named for its inventor, the German physicist Ernst Abbe, 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 wi ...

. The prism is named for its inventors, the French instrument maker Ph. Pellin and professor of physiological optics

André Broca André — sometimes transliterated as Andre — is the French and Portuguese form of the name Andrew, and is now also used in the English-speaking world. It used in France, Quebec, Canada and other French-speaking countries. It is a variation ...

. The prism consists of a four-sided block of glass shaped as a right

with 90°, 75°, 135°, and 60° angles on the end faces. Light enters the prism through face AB, 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 reflected b ...

from face BC, and exits through face AD. The

refraction In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomeno ...

of the light as it enters and exits the prism is 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, tro ...

of the light is deviated by exactly 90°. As the prism is rotated around an axis O, the line of intersection of bisector of ∠BAD and the reflecting face BC, the selected wavelength which is deviated by 90° is changed without changing the geometry or relative positions of the input and output beams. The prism is commonly used to separate a single required wavelength from a light beam containing multiple wavelengths, such as a particular output line from a multi-line

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...

due to its ability to separate beams even after they have undergone a non-linear frequency conversion. For this reason, they are also commonly used in optical

atomic spectroscopy Atomic spectroscopy is the study of the electromagnetic radiation absorbed and emitted by atoms. Since unique elements have characteristic (signature) spectra, atomic spectroscopy, specifically the electromagnetic spectrum or mass spectrum, is appl ...

.Svanberg, S. (2004), ''Atomic and Molecular Spectroscopy''.

References

{{DEFAULTSORT:Pellin-Broca prism Prisms (optics)