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| Light is produced when electrons in a substance have been energized from an outside source, and return from the energized state to their original state. Light is a form of electromagnetic wave with an extremely short wavelength, and is divided according to its wavelength into visible light and light that is invisible to the eye (infrared, ultraviolet). |
| How is Light Produced If you kick a soccer ball, it falls back to earth and raises dust where it hits. This is something like the way light is produced. The electrons in a substance (the soccer balls) receive external energy (a kick) and attain a high energy state. Then when they return to their original state this energy is released, producing light (dust). |
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| Electrons glow and go out one by one, but because substances contain vast numbers of electrons the overall material appears to shine continuously. The energy that is responsible for producing the light may be electrical energy, kinetic energy, thermal energy or some other kind. And the energy added to the substance may be converted not only into light, but depending on conditions may also be converted into heat, or into kinetic energy, and so on. |
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| How Do Light Bulbs and Fluorescent Tubes Shine? Light Bulbs Electricity flows through a filament and heats it. The electrons pick up the thermal energy in the filament and produce light. |
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| Fluorescent Tubes Light flows through a filament and heats it. The kinetic energy generated in the electrons is picked up by a mercury vapor which generates light in the form of ultraviolet radiation. The energy from this ultraviolet light is picked up by fluorescent substances painted onto the inside of a glass tube, and these substances then produce visible light. |
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| What is Light? |
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Light consists of waves called electromagnetic waves, like radio waves or X-rays. It travels at a speed of about 300,000 kilometers per second. The 'wavelength' of light refers to the distance between one peak and the next peak of the wave, or from one valley to the next valley. |
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