Bring on the Heat
Probably the most common way to energize atoms is with heat, and this is the basis of incandescence. If you heat up a horseshoe with a blowtorch, it will eventually get red hot, and if you heat it enough it gets white hot. Red is the lowest-energy visible light, so in a red-hot object the atoms are just getting enough energy to begin emitting light that we can see. Once you apply enough heat to cause white light, you are energizing so many different electrons in so many different ways that all of the colors are being generated -- they all mix together to look white, as explained in one of the sections below.Heat is the most common way we see light being generated -- a normal 75-watt incandescent bulb is generating light by using electricity to create heat. However, there are lots of other ways to generate light, some of which are listed below:
- Halogen lamps - Halogen lamps use electricity to generate heat, but benefit from a technique that lets the filament run hotter.
- Gas lanterns - A gas lantern uses a fuel like natural gas or kerosene as the source of heat.
- Fluorescent lights - Fluorescent lights use electricity to directly energize atoms rather than requiring heat.
- Lasers - Lasers use energy to "pump" a lasing medium, and all of the energized atoms are made to dump their energy at the exact same wavelength and phase.
- Glow-in-the-dark toys - In a glow-in-the-dark toy, the electrons are energized but fall back to lower-energy orbitals over a long period of time, so the toy can glow for half an hour.
- Indiglo watches - In Indiglo watches, voltage energizes phosphor atoms.
- Chemical light sticks - A chemical light stick and, for that matter, fireflies, use a chemical reaction to energize atoms.
