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Maxwell2D: Single pixel, two frequencies

Dielectric constant distribution

A small point is illuminated by two different frequencies simultaneously, one with five times the frequency of the other but half the amplitude. The scattered energy is much less than the incident energy, so the scattered amplitude in the animation is shown at 50 times its true amplitude (although the colours in the Poynting vector of the total and scattered fields are correct relative to each other). It can be seen that the high frequency component of the radiation is scattered much more efficiently than the low frequency component: the amplitude is proportional to the frequency squared (and hence intensity to frequency to the fourth power): this is known as Rayleigh scattering and explains why the sky is blue: sunlight contains all frequencies of visible light, but blue light has a higher frequency than red light so is scattered more readily. Wikipedia link: Rayleigh scattering

Electric field animation

This is an animation of the component of the electric field out of the plane of the page.

Average Poynting vector

The direction in which energy is travelling at any instant is proportional to the cross product of the electric and magnetic fields, known as the Poynting vector. The arrows show the direction of the Poynting vector averaged over the simulation, while the colours show its strength.