Re: how does the laser in a laser printer discharge the photoconductive drum?

Greetings:

The How Stuff Works web site has an excellent discussion about
laser printers along with illustrations.

http://howstuffworks.lycoszone.com/laser-printer.htm

Simple answer - Albert Einstein
won his Nobel Prize in physics for the Photoelectric Effect
which demonstrated that a photon of light can knock off an electron
from a metal surface. Thus laser light can discharge a charged surface.

The following text is taken from the web site.
QUOTE - The Basic Process
The primary principle at work in a laser printer is static electricity,
the same energy that makes clothes in the dryer stick together or a
lightning bolt travel from a thundercloud to the ground. Static
electricity is simply an electrical charge built up on an insulated
object, such as a balloon or your body. Since oppositely charged atoms
are attracted to each other, objects with opposite static electricity
fields cling together.

A laser printer uses this phenomenon as a sort of "temporary glue."
The core component of this system is the photoreceptor, typically a
revolving drum or cylinder. This drum assembly is made out of highly
photoconductive material that is discharged by light photons.
END QUOTE

Best regards, Your Mad Scientist
Adrian Popa