# 阿贝常数

## 定义：

（也称V数或v数）描述一个光学介质的折射率和色散能力的比值的常数。高V数表示对所有波长的折射近似相等（棱镜的色散较小）。

$V_d = \frac{n_d - 1}{n_f - n_c}$

Abbe condenser

## Definition:

(also V-value or v-value). The constant of an optical medium that describes the ratio of its refractivity to its dispersion. A high V-value indicates more nearly equal refraction at all wavelengths (less rainbow from a prism).

$V_d = \frac{n_d - 1}{n_f - n_c}$

where $V_d$ = V-value at $\lambda$ = 588 nm, $n_f$ = index of refraction at $\lambda$ = 486 nm, $n_c$ = index of refraction at $\lambda$ = 656 nm, and $n_d$ = index of refraction at $\lambda$ = 588 nm. The reciprocal of dispersive power.