Luminosity - The Emission of Light

Electromagnetic waves are produced by exciting the electrons in atoms. This is done by adding energy to the atom. You can think of the electrons in the atom as being bound to the nucleus by springs. When you add energy these electrons start to move up and down. These vibrations create ElectroMagnetic Waves. The more energy that is put into the atom the higher the energy the EM waves that are created will have. We put EM waves into different categories depending on how much energy they have. CLICK HERE to learn more about this. Note that this is a very crude analogy, but it may help you think about how EM waves are created.

The sun is an example of an object that emits light. Fusion provides the energy that excites the atoms that make up the sun. These atoms then emit light at all different frequencies.

How do scientists measure how much light is emitted from a luminous object? Early scientists created a unit for measuring the amount of light called a candela (cd). This was the amount of light that was emitted by a standard candle. If two standeard candles were lit then there would be two candelas of light. Can you see why scientists now might have a problem with measuring the intensity of light using candles? Scientists also use lumens to measure the rate at which light is emitted from a source.The lumen is The International System unit of luminous flux, and is equal to the light emitted in a unit solid angle by a uniform point source of one candela.

How do we measure the amount of light that falls on an object? Click Here to find out.