Grade 10 Physics - Light Production

incandescense

* Producing light as a result of high temperature.
* Very inefficient, only 5-10% of electricity used is being converted to visible light.
* Ex: incandescent light bulb, burning candle.

light from electric discharge

* Light produced by an electric current passing through a gas.
* Electricity causes gas to glow.
* Ex: lightning, neon signs, Geissler tubes.

phosphorescence

* Absorbs UV light, releases low-energy visible light.
* Ex: glow-in-the-dark toys

fluorescence

* Mercury gas atoms are excited by electrical flow in tube, and electrons produce UV light when they fall back to their ground state.
* Phosphorescent coating absorbs UV light and releases energy in the form of visible light.
* Ex: fluorescent light bulbs.

chemiluminescence

* Almost no heat produced.
* Production of light as a direct by-product of chemical reaction.
* Ex: glow sticks.

bioluminescence

* Chemiluminescence occurring in living organisms.
* Ex: fireflies, glow-worms.

triboluminescence

* Production of light when certain crystals are scratched, crushed, or rubbed.
* Ex: eating hard candy.

light emitting diode (LED)

* Highly energy efficient electronic device that allows electrical current in only one direction, using a semiconductor like silicon.
* Ex: Christmas lights, LED light bulbs, indicator lights, traffic lights.