Total Internal Reflection

When light is incident upon a medium of lesser index of refraction, the ray is bent away from the normal, so the exit angle is greater than the incident angle. Such reflection is commonly called "internal reflection". The exit angle will then approach 90° for some critical incident angle θ_c, and for incident angles greater than the critical angle there will be total internal reflection.

当光入射到折射率较小的介质时，光线会偏离法线，因此出射角大于入射角。这种反射通常称为‘全内反射’。当入射角达到临界角θc时，出射角将接近90°，对于大于临界角的入射角，将发生全内反射。

The critical angle can be calculated from Snell's law by setting the refraction angle equal to 90°. Total internal reflection is important in fiber optics and is employed in polarizing prisms.

临界角可通过斯涅尔定律计算，当折射角等于90°时。全内反射在光纤技术中具有重要作用，并用于偏振棱镜。

For any angle of incidence less than the critical angle, part of the incident light will be transmitted and part will be reflected. The normal incidence reflection coefficient can be calculated from the indices of refraction. For non-normal incidence, the transmission and reflection coefficients can be calculated from the Fresnel equations.

对于任何小于临界角的入射角，部分入射光将被透射，部分将被反射。正常入射时的反射系数可以从折射率计算得出。对于非正常入射情况，透射和反射系数可以从菲涅尔方程计算得出。

If values for n₁ and n₂ are entered above, the critical angle θ_c for total internal reflection will be calculated. (For example, θ_c = 48.6° for water and air.) But the angle for total internal reflection can be measured and used to determine the index of refraction of a medium. If a new value of θ_c is entered above, then the corresponding value of n₁ will be calculated.

如果输入了n₁和n₂的值，将计算全内反射的临界角θₐ。（例如，水和空气的θₐ为48.6°。）但全内反射的角可以被测量并用来确定介质的折射率。如果输入了新的θₐ值，则会计算对应的n₁值。