How does fire emit light (the sun, a candle, a fire, etc.)?


How does fire emit light (the sun, a candle, a fire, etc.)?

In: Physics

16 Answers

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All atoms above absolute zero (think of your freezer at home, it’s even colder than that), jiggle. The warmer things are, the more those atoms jiggle around.

Atoms have a core of protons and neutrons, and a shell of electrons. The core is really small, and the electrons form shells at different distances from the center. The closer it is to the core, the more energy there is holding it in place.

When you jiggle atoms, electrons from one atom are hitting the electrons of other atoms. When they hit hard enough, an electron is bumped to a further shell and the energy holding it in is let go. It’s like releasing a stretched elastic band, or dropping a coin from the top of a bridge. This creates electromagnetic energy. The more you jiggle, the more powerful (shorter wave) it is.

At lower temperatures, atoms close to each other radiate radio waves and infrared. Get hotter, and you get light. Even hotter, UV rays or even X-rays. The hotter the atoms get, the faster and harder they jiggle, and electrons fly more and more.

When you light something on fire, you are making it (or the gas that burns) just the right temperature to show that color. Cooler flames are red or yellow, warmer flames are green or blue, and we know this because blue light has a shorter (higher energy) wavelength than red light.

Tl;dr: Jiggling makes warm stuff make light.

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