A stroboscope, also known as a strobe, is an instrument
used to make a cyclically moving object appear to be slow-moving, or
stationary. The principle is used for the study of rotating, reciprocating, oscillating or vibrating objects. Machine parts and vibrating strings are common examples.
Intense flashing/pulsing light of various frequencies can trigger epileptic seizures in people who suffer from photosensitive epilepsy