Reflection and Transmission

反射与透射

External Reflection

外部反射

进入全反射

Fresnel's equations describe the reflection and transmission of electromagnetic waves at an interface. That is, they give the reflection and transmission coefficients for waves parallel and perpendicular to the plane of incidence. For a dielectric medium where Snell's Law can be used to relate the incident and transmitted angles, Fresnel's Equations can be stated in terms of the angles of incidence and transmission.

菲涅耳方程描述电磁波在界面处的反射和透射。也就是说，它们给出了与入射面平行和垂直的波的反射和透射系数。对于可以利用斯涅尔定律来关联入射角和透射角的介电体介质，菲涅耳方程可以表示为入射角和透射角的函数。

Fresnel's equations give the reflection coefficients:

菲涅耳方程给出了反射系数：

= and

等于和

中文译文中的待填/计算数值依次对应：1：rp。实际数值以上方原输入框为准。

The transmission coefficients are

透射系数为

= and

等于和

中文译文中的待填/计算数值依次对应：1：tp。实际数值以上方原输入框为准。

Note that these coefficients are fractional amplitudes, and must be squared to get fractional intensities for reflection and transmission.

请注意，这些系数是分数振幅，必须平方以得到反射和透射的分数强度。

You can choose values of parameters which will give transmission coefficients greater than 1, and that would appear to violate conservation of energy. (For example, try light incident from a medium of n₁=1.5 upon a medium of n₂=1.0 with an angle of incidence of 30°.) But the square of the transmission coefficient gives the transmitted energy flux per unit area (intensity), and the area of the transmitted beam is smaller in the refracted beam than in the incident beam if the index of refraction is less than that of the incident medium. When you take the intensity times the area for both the reflected and refracted beams, the total energy flux must equal that in the incident beam. For further details, see Jenkins and White.

你可以选择参数值，使得透射系数大于1，这似乎违反了能量守恒。（例如，尝试光从折射率n1=1.5的介质入射到折射率n2=1.0的介质，入射角为30°。）但透射系数的平方给出了单位面积的透射能量流（强度），如果折射率小于入射介质的折射率，则折射束的横截面积小于入射束。当计算反射束和折射束的强度乘以面积时，总能量流必须等于入射束的能量流。更多细节，请参见Jenkins和White。

Checking out conservation of energy in this situation leads to the relationship

检验这种情况下能量守恒关系得出