A light source is a natural or man-made object that emits one or more wavelengths of light.
Natural light sources include:
The Sun is the most important natural light source in our lives and emits every wavelength of light in the visible spectrum.
Celestial sources of light include other stars, comets and meteors.
Other natural sources of light include lightning, volcanoes and forest fires.
There are also bio-luminescent light sources including some species of fish and insects as well as types of bacteria and algae.
Man-made light sources include:
Man-made light sources of the most simple type include natural tars and resins, wax candles, lamps that burn oil, fats or paraffin and gas lamps
Tungsten lights: These are a type of incandescent source which means they radiate light when electricity is used to heat a filament inside a glass bulb.
Halogen bulbs: These are more efficient and long-lasting versions of incandescent tungsten lamps and produce a very uniform bright light throughout the bulb’s lifetime.
Fluorescent lights: These are non-incandescent sources of light. They generally work by passing electricity through a glass tube of gas such as mercury, neon, argon or xenon instead of a filament. Fluorescent lamps are very efficient at emitting visible light, produce less waste heat, and typically last much longer than incandescent lamps.
LED lights: An LED (Light Emitting Diode) is an electroluminescent light source. It produces light by passing an electrical charge across the junction of a semiconductor. An LED light typically emits a single colour of light which is composed of a very narrow range of wavelengths.
Made-made lights can emit a single wavelength, bands of wavelengths or combinations of wavelengths.