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Definitely anecdotal.

This friend is hypermetropic, and uses reading glasses. He doesn't have major issues facing car headlights, or using a torch (the one with a bulb - not a white LED). Yet place him in front of a TV/Computer screen, and he'll develop an ache in the eye sockets in no time.

I understand an electric torch, an incandescent bulb, a car lamp are all DC types, whereas a TV/Computer screen is fast changing AC.

Are human eyes equally sensitive to light from an AC, and a DC lamp?

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Incandescent bulb also can use ac. Tv screens are different case altogether. It is a flickering light. –  WYSIWYG Jul 14 '13 at 18:55
    
I'm not great with electronics, but don't all devices use DC? Computers and TVs require AC adaptors to convert the AC power supply to a usable DC signal. –  Brandon Invergo Jul 14 '13 at 22:23
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Depends on the device. Many lamps work on AC. Fans and motors work on AC. Incandescent lamps work on the principle of electrical heating which both types of current can do. Semiconductor devices generally use DC because direction of the current is important. TV screens are not continuous light; it is a kind of flickering light. In a previous post, this has been discussed with respect to cats and dogs. You may find it useful. –  WYSIWYG Jul 15 '13 at 4:41
    
@WYSIWYG: The link to the other post was helpful. ty (+: –  Everyone Jul 15 '13 at 17:01
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I doubt that it's what kind of electricity provides the power -- rather what wavelengths of the light are emitted. –  kmm Jul 15 '13 at 18:56
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