Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: paul.fr on 06/07/2007 08:43:04

Title: photocopiers and green light
Post by: paul.fr on 06/07/2007 08:43:04

the photocopiers at work all use a green light when scanning the paper, why green?

Title: photocopiers and green light
Post by: DoctorBeaver on 06/07/2007 10:44:21

Would green, perchance, be in the middle of the visible spectrum?

Title: photocopiers and green light
Post by: dentstudent on 06/07/2007 10:52:11

From "how stuff works"

Lamp and Lenses
Making a photocopy requires a light source with enough energy to boot electrons out of the photoconductive atoms. What wavelengths of light can do this? It turns out that most of the visible spectrum of light contains enough energy to drive the process, especially the green and blue end of the spectrum. Anything lower than the red portion of the visible spectrum doesn't have enough gusto to activate the photoconductor. And, although UV light has more than enough firepower to make a photocopy, it can be very damaging to our eyes and skin. This is why photocopiers use a plain old incandescent or fluorescent bulb to flash light onto the original document.