- #1
nonequilibrium
- 1,439
- 2
Say we have an electromagnetic wave propagating inside a dielectric material. Of course physically this material will radiate, due to the little electrons being excited by the wave (their wiggling is also the physical cause of the [tex]\epsilon \neq \epsilon_0[/tex]), and oscillating dipoles radiate. And of course in usual situations this can and should be ignored, but my question is something else: how come in simple treatments of dielectric materials, there is no radiation, none at all? For example, in my book of Griffiths, in chapter 9 we deduce (the properties of) the reflection and refraction of light on a dielectric surface, but it turns out the energy going in (in the initial light beam), is the same as the energy in the reflected beam + the transmitted beam. In other words, the dielectric isn't radiating any energy. This would not seem weird if we had made that assumption beforehand, but it seems that we never made such an approximation. So even though usually negligible, shouldn't there be a certain amount of radiation due to the oscillating dipoles?
Apparently the equations of Maxwell for matter don't account for the radiation caused by the time-variation of [tex]\vec P \quad \textrm{ in } \quad \vec D = \epsilon_0 \vec E + \vec P,[/tex]
is this correct? (if not correct, how do you explain the first paragraph?)
Apparently the equations of Maxwell for matter don't account for the radiation caused by the time-variation of [tex]\vec P \quad \textrm{ in } \quad \vec D = \epsilon_0 \vec E + \vec P,[/tex]
is this correct? (if not correct, how do you explain the first paragraph?)