What is Light, baby don’t hurt me … Production of light What is Light, baby don’t hurt me …

Learning goals We are learning the different ways light is produced.

Geometric optics terms NON-LUMINOUS – objects that do not produce light We see them because light reflects off them to our eyes Ex. moon LUMINOUS – objects that produce/emit light

luminous NATURAL – produce light without human intervention Sun, lava, northern lights, lightning, firefly

luminous Artificial – light produced and controlled by humans Car lights, neon signs, flashlights

Production of light Converted energy Recall: Law of Conservation of Energy Energy cannot be created or destroyed. It can only change/convert from one form to another Example: Input Energy Form Converter Output Energy Form Chemical Light, Heat

Methods of production

Incandescence Light from a heated object Various methods of heating Adding thermal energy Friction Electricity Chemical energy

Electric discharge Electrons get excited and move to higher energy state due to collisions As electrons move back to smaller orbit, energy is released Natural Lightning, static, northern lights Artificial Current passed through noble gas

fluorescence Emission of light when exposed to ultraviolet (UV) light Phosphors – material that is excited by UV light emit white light How it works: Electric current through gas Mercury emits UV UV hits phosphor coating

phosphorescence Some phosphors absorb UV or visible light, store the energy and emit it later as visible light Glow in the dark stickers

chemiluminescence Result of chemical reaction Little/no heat produced – cold light Ex. Glow sticks

bioluminescence Chemiluminescence in living organisms Ex. Glow worms, fire flies

triboluminescence Light produced by friction specifically in crystals through the breaking of chemical bonds in the material. Lifesavers in the dark – does it make a spark!? Peeling two pieces of duct tape apart

Light emitting diode (LED) electroluminescence a material emits light after passing an electric current through it. Christmas lights – doesn’t emit heat, doesn’t require a filament, more energy efficient.

“laser” Laser Video Light Amplified by Stimulated Emission of Radiation Electromagnetic waves emitted exactly the same (direction and energy) Pure in colour, very intense and concentrated into one narrow beam.

Learning goals We are learning the different ways light is produced.