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
Chemical
Converter
Output Energy Form
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.