Illusion means overrefinement of the senses. Illusions may occur with any of the human senses, but vision often dominates the other senses and an illusion that is something to do with visual sense is known as optical illusion. For  optical illusions, information gathered by the eye is processed in the brain to give a perception that does not tally with a physical measurement of the stimulus source.

Earlier, I shared a video on optical illusion: Resonance Experiment: Fun With Chladni Patterns where the sand-covered surface is made to vibrate and the sands get collected in the region that has least motion which gives rise to simple-to-complex geometrical patterns depending on the intensity of frequency.

The video below is another awesome compilation of optical illusions from a YouTube user brusppup which includes the previously shared Chladni patterns or Chladni’s figures.