Sources of Light
Cards (8)
- Types of Light
- A luminous object produces its own light
- Sun, flashlights, fire, lit match
- A non-luminous object does not produce its own light, it can only be seen by light reflecting off of it
- Trees, cars, jeans, the moon
- Incandescence
- Produces light as a result of high temperature. Very hot = will glow
- Stove burner
- incandescent light bulbs: a thin wire filament glows as electricity passes through it and becomes so hot it gives off light
- Increasing temp red-orange-yellow-white-blue)
- Electric discharge
- Producing light by passing an electric current through a gas causing a gas to glow
- Noble gases emit different colors: ne=red ar=violet kr=light grey he=gold
- Neon signs, street lights, lightning bolts
- Fluorescence
- Producing light by absorbing UV light and immediately releasing the energy as visible light
- fluorescent lights make use of both electric discharge and fluorescence
- A compact fluorescent light is filled with mercury vapour and coated with fluorescent material
- Phosphorescence - Luminescence
- Producing light by absorbing UV light and emitting it as visible light over a long period of time
- Varies from seconds to days
- Glow-in-the-dark materials are coated with phosphors, special materials that give off light through phosphorescence
- Chemiluminescence - Luminescence
- Producing a light as a direct by product of a chemical reaction with little heat being produced
- Glow sticks: two chemicals mix when the vial inside is broken, causing a chemical reaction and producing visible light
- Bioluminescence - Luminescence
- Producing light in a living organism through chemical reactions using enzymes
- Used to lure prey, protect from predators or attract mates
- Light-Emitting Diode (LED)
- Electrical component made of semiconductors that produces light when current comes through it (current can flow in one direction making light but little heat)
LEDs don’t produce much heat & are very efficient