Normal Reflection Coefficient

The reflectivity of light from a surface depends upon the angle of incidence and upon the plane of polarization of the light. The general expression for reflectivity is derivable from Fresnel's Equations. For purposes such as the calculation of reflection losses from optical instruments, it is usually sufficient to have the reflectivity at normal incidence. This normal incidence reflectivity is dependent upon the indices of refraction of the two media.

For light from a medium of index n1 = 对于来自折射率为n₁的介质的光， 中文译文中的待填/计算数值依次对应：1：n1。实际数值以上方原输入框为准。

normally incident upon a medium of index n2 = 通常入射到折射率为n₂的介质上 中文译文中的待填/计算数值依次对应：1：n2。实际数值以上方原输入框为准。

the reflectivity is 反射率是

= %

The reflection coefficients can be used to calculate the amount of light transmitted through a medium if the only losses are reflection losses.

反射系数可以用来计算光通过介质时的透射量，如果唯一损失仅是反射损失的话。

Reflected from first surface: % Transmitted into medium: % Reflected internally from second surface: % Transmitted through medium: % 第一表面反射：% 透入介质：% 第二表面内部反射：% 介质中透射：% 中文译文中的待填/计算数值依次对应：1：r1 2：t1 3：r2 4：t2。实际数值以上方原输入框为准。

This calculation of the transmission is not exactly correct since it neglects the contribution from multiple internal reflections in the medium. Since this contribution is proportional to the square and higher powers of the reflection coefficient, it can often be neglected. The reflection loss at a single surface may seem small, but with multiple lenses, it becomes an unacceptable loss. Anti-reflection coatings are used to diminish the losses.