principal dispersion (original) (raw)

Author: the photonics expert (RP)

Definition: a crude measure for chromatic dispersion of a transparent optical material

Category: general optics

• optical properties of materials
  • absorptance
  • absorption coefficient
  • absorption length
  • birefringence
  • chromatic dispersion
  • dichroism
  • emissivity
  • group delay dispersion
  • group index
  • group velocity
  • nonlinear index
  • opacity
  • optical activity
  • optical density
  • polarization beat length
  • principal dispersion
  • propagation losses
  • refractive index
  • Sellmeier formula
  • thermo-optic effect
  • transparency
  • (more topics)

Related: chromatic dispersionrefractive indexAbbe number

Formula symbol: ($n_\textrm{F} - n_\textrm{C}$)

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DOI: 10.61835/u26 Cite the article: BibTex BibLaTex plain textHTML Link to this page! LinkedIn

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Contents

What is Principal Dispersion?

The principal dispersion is a rather crude measure for chromatic dispersion of an optical material in the visible spectral region, which was developed in the early years of optics. It is simply the difference of refractive indices between two specific standard spectral lines of hydrogen:

• the F line at 486.1 nm (blue)
• the C line at 656.3 nm (red)

The principal dispersion ($n_\textrm{F} - n_\textrm{C}$) appears in the definition of the Abbe number.

In photographic optics, the principal dispersion is often based on two somewhat different spectral lines of cadmium:

• the F' line at 480 nm (blue)
• the C' line at 643.8 nm (red)

Modern Dispersion Values

In modern technology, more comprehensive ways of characterizing chromatic dispersion are common. For example, a quantity like the refractive index, the group velocity or the group velocity dispersion is given as a function of wavelength. Another possibility is to use a Taylor expansion at a specific wavelength, including second-order and higher-order dispersion numbers.

Frequently Asked Questions

This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).

What is principal dispersion?

What is the principal dispersion used for?

The principal dispersion ($n_\textrm{F} - n_\textrm{C}$) is a key component in the definition of the Abbe number, a standard quantity used to characterize optical glasses and other materials.

How is chromatic dispersion quantified in modern optics?

Modern methods characterize chromatic dispersion more comprehensively, for example by specifying the group velocity dispersion as a function of wavelength, or by using a Taylor expansion around a certain wavelength to obtain second-order and higher-order dispersion parameters.

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