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Maxwell2D: Total internal reflection

Dielectric constant distribution

Consider light propagating in a medium of higher refractive index incident upon an interface to a medium with lower refractive index. If the angle beween the direction of propagation and the normal to the interface is greater than the critical angle then total internal reflection will occur. In the case shown, the refractive index of the first medium is n1 = 1.52 and of the second medium is n1 = 1. The critical angle is given by sin-1(n2/n1), which is 41° in this case. The angle of incidence is 45° so total internal reflection occurrs. This property is used in the prisms of bicycle reflectors and is easy to observe when looking through water into air. An evanescent wave occurs next to the interface in the second medium: its amplitude decays exponentially away from the surface. If we introduce a new medium in the region of the evanescent wave, we get frustrated total internal reflection.
Wikipedia links: Total internal reflection, Evanescent wave

Electric field animation

Time-averaged Poynting vector

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