Stroboscope

Strob´o`scope

n.	1.	An instrument for studying or observing the successive phases of a periodic or varying motion by means of light which is periodically interrupted.
	2.	An optical toy similar to the phenakistoscope. See Phenakistoscope.

Noun

stroboscope - scientific instrument that provides a flashing light synchronized with the periodic movement of an object; can make moving object appear stationary

Synonyms: strobe, strobe light