How does laser printer works?
When a text or image is entered into the CPU, it makes a series of varying voltages. This controls a LED (light emitting diode) in the printer. This produces flashes of laser, when it falls on a charged photo conducting drum. The area corresponds the text or image will either be neutralized or oppositely charged. A toner which has the similar charge as the background is sprayed onto it. It only sticks to the text or image and is repelled by the background.