English: This is a simulation of diffraction effects around a circular obstacle (green line on the video, viewed from the side) illuminated by short pulses from the left side of the screen. The pulses are scalar waves composed from 51 harmonic plane waves. The obstacle is an (almost) opaque and non-reflective disk whose radius is 20 median wavelengths of the pulse. The obstacle is simulated by placing two layers of point sources across the disk and fitting their amplitudes so that near the front of the disk their collective field is zero and near the back of the disk their field cancels out the incident wave. The gradient at the bottom of the image is a color key that is linear with respect to the amplitude.