菲涅尔公式讨论光波反射和折射时振幅的变化

Discussion on the Change of Amplitude of Light Wave in Reflection and Refraction Using Fresnel′s Formula

光波在两种均匀各向同性媒质界面上发生反射和折射时,入射波、反射波、折射波的振幅、位相、能流密度等,均可以用电磁波理论中的菲涅尔公式给予分析.利用菲涅尔公式,讨论了光波由光疏介质进入光密介质和由光密介质进入光疏介质两种情况下,反射光和折射光的振幅变化,发现当光从光密介质进入光疏介质时,振幅变大,即振幅不满足“能量守恒”的一种有趣现象,利用能流密度的概念对这种现象进行讨论和证明,让学生深入理解光能量与振幅平方成正比的适用范围,进一步对能量守恒定律的普适性有更深刻的认识.

When light waves are reflected and refracted at the interface of two uniform and isotropic media,the amplitude,phase,and energy density flow of incident waves,reflected waves,and refracted waves can all be analyzed by the Fresnel s formulae in electromagnetic wave theory.Fresnel s formulae to discuss the amplitude changes of reflected light and refracted light when the light wave enters the optically dense medium from the optically thin medium and the optically dense medium enters the optically dense medium.When the medium enters the optically thin medium,the amplitude becomes larger,that is,an interesting phenomenon in which the amplitude does not meet the“energy conservation”law.This phenomenon is discussed and proved by using the concept of energy density flow,so that students can deeply understand the application range of light energy proportional to the square of the amplitude,and have a deeper understanding of the universality of the law of conservation of energy.