A fascinating optical illusion?

[mathgrant]

You know how your hand looks blurry when you move it quickly?

When I move my hand quickly in front of my computer screen, it's not blurry. Instead, I catch many quick glimpses of "freeze frames" of my hand.

This seems to only happen when the screen displays light colors. Otherwise, it's plain old motion blur

How can this be explained?
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My logic puzzle blog

[Logain]

I would say you're seeing the effect of the monitor's refresh rate. A CRT flicker isn't visible to the naked eye since the cycle time is too short, but waving your hand or a pen in front of it can give you an snapshot image since the monitor is refreshing at that moment. Have you ever watched your monitor through a digital camera?

[extropalopakettle]

Yes, it's a simple strobe effect. Happens with TV and even crappy fluorescent lights. A similar but even more fascinating effect: if you wave something in front of the light from a digital projector, you'll see multiples, but in different colors - red, green and blue. Works best if the prjector is projecting a white screen image, and the object is light colored. Happens because the digital projector switches rapidly between red, green and blue.

[jaap]

Instead of waving your hand over a tv or crt monitor, stretch a thin rubber band between your hands and twang it. The strobing screen shows the waves travelling along the band. Great fun when you're bored at work...

[Phil_The_Rodent]

I'm just sitting here quietly giggling about what your coworkers see as you frantically wave at your monitor.