A triangular prism is a fundamental and versatile optical component made from a transparent material, characterized by its geometric shape of two triangular bases and three rectangular lateral faces. It is one of the most common and simplest types of optical prisms.

Its operation is based on the principles of refraction and dispersion:

• Dispersion: This is its most famous property. When a beam of white light enters one of the rectangular faces at an angle, it is refracted (bent) upon entry and exit. Crucially, different wavelengths (colors) of light are refracted by different amounts. This causes the white light to spread out into its constituent spectral colors, creating a visible rainbow or spectrum. This effect is central to spectroscopy for analyzing light.

• Deviation and Reflection: A triangular prism can also be used to simply deviate a beam of light from its original path or, if the light strikes the internal faces at a sufficient angle (greater than the critical angle), it can act as a reflector using Total Internal Reflection (TIR), which is very efficient as it requires no mirrors or coatings.

• Materials: They are fabricated from various optical glasses (e.g., N-BK7 for visible light) or crystals (e.g., Fused Silica for UV, Calcium Fluoride for IR), chosen based on the required transmission wavelength and dispersion characteristics.

• Precision: For scientific and industrial applications, the prisms are manufactured to high precision. Key specifications include the apex angle, surface flatness (often to a fraction of a wavelength of light, e.g., λ/10), and surface quality (minimal scratches and digs).

• Spectroscopy: As the core component in spectrometers, spectrographs, and monochromators to separate light for chemical analysis, astronomy, and environmental monitoring.

• Demonstration and Education: Universally used in physics classrooms to vividly demonstrate the principles of refraction and the composition of white light.

• Beam Steering: In some laser and imaging systems, to deviate or displace a light beam.

• Component of Larger Systems: Often used as a building block within more complex optical assemblies like binoculars or periscopes.