Technology that Produces LightTechnology that Produces Light

1. Incandescence1. Incandescence – when objects are – when objects are heated enough, they glow.heated enough, they glow.

Ex. Incandescent Light BulbsEx. Incandescent Light Bulbs

– – electricity heats up metal filamentelectricity heats up metal filament

– – convert only 5% of energy into light!convert only 5% of energy into light!

22. Fluorescence . Fluorescence – chemicals absorb UV energy – chemicals absorb UV energy and change it into light. Different chemicals and change it into light. Different chemicals make different colours.make different colours.

Fluorescent Light Bulbs – Fluorescent Light Bulbs – electricity excites mercury electricity excites mercury and argon gas, which then and argon gas, which then makes white powdered makes white powdered coating glow. These are 20% coating glow. These are 20% efficient!efficient!

Phosphors – Chemicals that Phosphors – Chemicals that creates glow in the dark creates glow in the dark paint. paint.

Discharge lamps – electricity excites noble Discharge lamps – electricity excites noble gases, which then make different coloured gases, which then make different coloured phosphors in a pixel glow. (neon lights, phosphors in a pixel glow. (neon lights, plasma TV)plasma TV)

* LCD displays work differently - * LCD displays work differently - electricity electricity excites bands of chemicals which cause them to excites bands of chemicals which cause them to turn and let light from a fluorescent bulb pass turn and let light from a fluorescent bulb pass through a coloured filter (Monitors, clocks, TV).through a coloured filter (Monitors, clocks, TV).

3. Light Emitting Diode (LED)3. Light Emitting Diode (LED) – electricity flows – electricity flows through a semiconductor which then releases through a semiconductor which then releases light. Very efficient but expensive (back lights).light. Very efficient but expensive (back lights).

4. Chemoluminescence4. Chemoluminescence – light produced by a – light produced by a chemical reactions ex. glow stickschemical reactions ex. glow sticks

**Some animals can do this inside their bodies **Some animals can do this inside their bodies (called bioluminescence)(called bioluminescence)

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How would your life change if we didn’t have How would your life change if we didn’t have technology to make light?technology to make light?

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