Flash a light fast enough, and it stops looking like it's flashing at all
The flicker fusion threshold is the flash rate at which a blinking light stops registering as separate flickers and looks like it's glowing continuously, for humans that's roughly 50 to 90 times a second depending on brightness. It's why old fluorescent tubes, CRT screens and film projectors don't look like they're strobing. Peter Mark Roget described the underlying persistence-of-vision effect in an 1825 paper on spinning carriage wheels.