Is the red light effect in xerographic copiers the same concept behind red light…

Is the red light effect in xerographic copiers the same concept behind red lights in a darkroom? Does film have the same sort of properties?

Yes. The light sensitive particles in black-and-white photographic paper don’t respond to red light because the energy in a photon of red light doesn’t have enough energy to cause the required chemical change. In effect, electrons are being asked to shift between levels when the light hits them and red light can’t make that happen in the photographic paper. However, most modern black-and-white films are sensitive to red light because that makes roses and other red objects appear less dark and more realistic in the photographs.

Why do poles have to come in pairs?

Why do poles have to come in pairs?

There don’t appear to be any isolated poles in our universe, or at least none have been found. That’s just the way it is. As a result of this situation, the only way to create magnetism is through its relationship with electricity. When you use electricity to create magnetic fields, you effectively create equal pairs of poles—as much north pole as south pole.

Would placing a blue filter on a Xerox machine prevent it from making copies, si…

Would placing a blue filter on a Xerox machine prevent it from making copies, since blue light has more energy than red?

No. Blue light causes the photoconductor to conduct. When you use white light in a xerographic copier, it’s the blue and green portions of the light that usually do the copying. The red is wasted.

Does this photoconductor stuff have to do with why you can only develop film in …

Does this photoconductor stuff have to do with why you can only develop film in the dark?

Yes. Particles of light, photons, cause chemical changes in the film. You can work with some black-and-white films in red light because red light photons don’t have enough energy to cause changes in those films. However, color film and most modern black-and-white films require complete darkness during processing. If you expose them to any visible light, you’ll cause chemistry to occur.

How do color copiers work?

How do color copiers work?

They assemble 4 colors, yellow, cyan, magenta, and black together to form the final image. The photoconductor creates charge images using blue, red, green, and white illumination successively and uses those images to form patterns of yellow, cyan, magenta, and black toner particles. These particles are then superimposed to form the final image, which appears full color. Naturally, the photoconductor used in such a complicated machine must be sensitive to the whole visible spectrum of light.

As one of my readers (Tom O.) points out, most modern color copiers are essentially scanners plus color printers. They use infrared lasers to write the images optically onto four light-sensitive drums, one drum for each of the four colors (some systems reuse the same drum four times).

Can the electric current be taken out of the metal where the charge will not car…

Can the electric current be taken out of the metal where the charge will not carry?

While charges can move freely through a metal, allowing the metal to carry electric current, it’s much harder for charges to travel outside of a conductor. Charges can move through the air or through plastic or glass, but not very easily. It takes energy to pull the charges out of a metal and allow them to move through a non-metal. Most of the time, this energy requirement prevents charges from moving through insulators such as plastic, glass, air, and even empty space.