Technique · Fields
Ripple interference
Circular waves from several sources adding up on water, with the flat fans where crest meets trough.
Ripple interference is a field drawn for every pixel by the graphics chip. Every piece on Synapse Drip is made from a recipe that layers techniques like this one, and you can change any of it in the Studio.
Good to know
- A ripple tank, a shallow glass tray of water lit from above, is a standard school demonstration of wave interference because the crests cast visible shadows on a screen below.
- In the 1860s the Scottish physicist James Clerk Maxwell worked out that light itself is an electromagnetic wave, which explained why interference fringes appear with light just as with water.
- Where waves cancel, the water stays flat, and the flat places between two sources lie along hyperbolas, curves for which the difference of the distances to the two sources is constant.
- Thomas Young showed in about 1801 that light makes the same crossing fans as water waves when it passes through two narrow slits, which settled for a time that light is a wave.
- Noise-cancelling headphones use the same effect on purpose: they play a copy of the noise upside down, so that crests meet troughs and the sound cancels.
The mathematics
- Each source adds cos(k r - w t) / (1 + 3.20 r), with k = 2 pi / 0.060 of the picture's height; the amplitude falls with distance, as it does in a real wave whose energy spreads round a longer and longer ring.
- The crests of two sources reinforce where the difference of the two distances is a whole number of wavelengths, and cancel where it is half a wavelength more; each of those conditions is the equation of a hyperbola.
- With sources in a row the fans merge into beams, the way a diffraction grating sends each colour of light in its own set of directions.
In art
- Bridget Riley's black-and-white painting Current (1964), made of closely ruled waving lines, uses the same interference to make a flat surface seem to shimmer and flow.
- Claude Monet painted the surface of his water-lily pond over and over, for more than twenty years, because moving water turns one colour into endless detail.
More ways to use it
Related techniques
Nebula and stars · Liquid · Droplets · Network · Terrain and maps · Neuron · Order to chaos · Fractal tree