Prisms

棱镜

A refracting prism is a convenient geometry to illustrate dispersion and the use of the angle of minimum deviation provides a good way to measure the index of refraction of a material. Reflecting prisms are used for erecting or otherwise changing the orientation of an image and make use of total internal reflection instead of refraction.

折射棱镜是一种方便的几何结构，用于说明色散以及利用最小偏差角来测量材料的折射率。反射棱镜用于校正或改变图像的方向，并利用全内反射而不是折射。

White light may be separated into its spectral colors by dispersion in a prism.

白光可通过棱镜的色散作用分解为它的光谱颜色。

Prisms are typically characterized by their angle of minimum deviation d. This minimum deviation is achieved by adjusting the incident angle until the ray passes through theprism parallel to the bottom of the prism.

An interesting application of refraction of light in a prism occurs in atmospheric optics when tiny hexagonal ice crystals are in the air. This refraction produces the 22° halo commonly observed in northern latitudes. The fact that these ice crystals will preferentially orient themselves horizontally when falling produces a brighter part of the 22° halo horizontally to both sides of the sun; these bright spots are commonly called "sundogs".

光在棱镜中的折射现象在大气光学中也有有趣的应用。当空气中存在微小的六边形冰晶时，就会发生这种折射，产生常见的22° halo，这在北半球经常被观察到。这些冰晶在下落时倾向于水平取向，导致22° halo的水平两侧出现更明亮的部分；这些明亮的斑点通常被称为‘ sundogs ’。

棱镜通常以其最小偏差角d来表征。通过调整入射角，使光线通过棱镜时与棱镜底部平行，即可实现最小偏差。

Prisms

棱镜

The angle of minimum deviation for a prism may be calculated from the prism equation. Note from the illustration that this minimum deviation occurs when the path of the light inside the prism is parallel to the base of the prism. If the incident light beam is rotated in either direction, the deviation of the light from its incident path caused by refraction in the prism will be greater.

棱镜的最小偏向角可通过棱镜方程计算。从图示可以看出，当光线在棱镜内的路径平行于棱镜的底面时，出现最小偏向角。如果入射光束向任一方向旋转，由于棱镜中的折射，光线偏离其入射路径的程度将增大。

White light may be separated into its spectral colors by dispersion in a prism.

白光可通过棱镜的色散作用分解为它的光谱颜色。