How a parabolic antenna works

This new episode of #shorts shows the basic principle of a parabolic antenna. A circular wave is emitted from the parabola's focus, and becomes a planar wave upon reflection on the parabola. Therefore, this part of the wave does hardly disperse when traveling to the right, allowing it to cover long distances with very little loss of energy. By the same principle, a planar wave is reflected towards the focus, concentrating its energy in one point. This can be observed on the part of the wave reflected on the right boundary, due to imperfect absorbing boundary conditions used there. The colors indicate the energy of the wave: blue means low energy, red means high energy.

Music: Prelude No. 6 by Chris Zabriskie is licensed under a Creative Commons Attribution 4.0 licence. https://creativecommons.org/licenses/...
Source: http://chriszabriskie.com/preludes/
Artist: http://chriszabriskie.com/

See also https://images.math.cnrs.fr/Des-ondes... for more explanations (in French) on a few previous simulations of wave equations.

The simulation solves the wave equation by discretization. The algorithm is adapted from the paper https://hplgit.github.io/fdm-book/doc...
C code: https://github.com/nilsberglund-orlea...
https://www.idpoisson.fr/berglund/sof...
Many thanks to my colleague Marco Mancini for helping me to accelerate my code!