Dispersion

色散

Chromatic dispersion is the change of index of refraction with wavelength. Generally the index decreases as wavelength increases, blue light traveling more slowly in the material than red light. Dispersion is the phenomenon which gives you the separation of colors in a prism. It also gives the generally undesirable chromatic aberration in lenses. Usually the dispersion of a material is characterized by measuring the index at the blue F line of hydrogen (486.1 nm), the yellow sodium D lines (589.3 nm), and the red hydrogen C line (656.3 nm). The dispersion is measured by a standard parameter known as Abbe's number, or the v value or V number, all of which refer to the same parameter:

色散是折射率随波长的变化。通常，折射率随着波长的增加而减小，蓝光在材料中比红光传播得更慢。色散是导致棱镜中颜色分离的现象。它也导致透镜中通常不希望出现的色差。通常通过测量材料在氢的蓝F线（486.1 nm）、钠的黄D线（589.3 nm）和氢的红C线（656.3 nm）处的折射率来表征材料的色散。色散通过一个标准参数来测量，称为阿贝数，或v值或V数，它们都指的是同一个参数：

Data from Serway & Jewett

Data from Serway & Jewett（专名或术语）

Blue light travels more slowly than red light in transparent media.

在透明介质中，蓝光比红光传播得更慢。

The effect of dispersion on the focal length of a lens can be examined by calculating the change in the focal length with wavelength. The table below starts with a biconvex lens designed to have a focal length of 10.0 cm for violet light (400 nm) in crown glass. The focal lengths shown are calculated from the lensmakers equation with radii of curvature 10.62 cm for both surfaces.

色散对透镜焦距的影响可以通过计算波长变化时焦距的变化来研究。下表从一个设计用于在火石玻璃中对 violet 光（400 nm）有 10.0 cm 焦距的双凸透镜开始。表中所示的焦距是根据透镜公式计算得出的，两面的曲率半径均为 10.62 cm。

Medium 介质	Violet 400 nm 紫光 400 nm	Red 650 nm 红光650纳米
Crown glass 王冠玻璃	10.00	10.37
Acrylic 聚丙烯酸酯	10.46	10.87
Fused quartz 熔融石英	11.30	11.58

Chromatic aberration arising from dispersion.

由于色散引起的色差

Separation of colors by a prism is an example of dispersion.

棱镜分色是色散的一个例子。

Example of Dispersion

色散示例

Dispersion in optical glasses is typically characterized by index of refraction values at three standard wavelengths.

光学玻璃的色散通常通过三个标准波长的折射率值来表征。

Note that a low v value implies high dispersion.

注意，低的 v 值意味着高分散性。