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Producing Light

Producing Light

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Producing Light

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  1. Producing Light Types of Light

  2. Light is a form of Energy Other forms of energy include: • Chemical • Nuclear • Electrical • Kinetic (movement) • Thermal (heat)

  3. The Law of Conservation of Energy Energy cannot be created or destroyed = The First Law of Thermodynamics

  4. Natural vs. Artificial Light • The most important source of light is the Sun • Light produced by the Sun or other stars is natural light • Light produced by human technology is artificial light

  5. Luminous vs. Non-Luminous • A luminous light source produces its own light (it is non-illuminated) • A non-luminous light source does not produce its own light (it is illuminated) • A non-luminous light source reflects or refracts light from another source

  6. What is the Scientific Definition of Light? • Technically speaking, only the range of electromagnetic radiation in the visible spectrum is classified as “light” • Therefore, the scientific definition of light is: “A form of energy that you can detect with your eyes”

  7. There are Two Types of Light Luminous • Objects that emit their own light Non-luminous • Objects that do not emit their own light

  8. There are Eleven Types of Luminous Sources There are Three Types of Non-luminous Sources

  9. Luminous Sources (1) Incandescence • Light is produced by an object, such as a metal, that is at a very high temperature • Current flows through the filament (tungsten) in a light bulb, and some of the energy is emitted as light • Very inefficient, only 5% of the electrical energy is converted to light, the rest is heat

  10. Luminous Sources (2) Fluorescence • Light emitted by some substances when exposed to electromagnetic radiation • Fluorescent light tubes are full of gas and coated with a white powder called a phosphor • Electric current energizes the gas, which emits UV radiation • UV hits the phosphor, which glows and emits light • Compact fluorescent bulbs are about 20% efficient

  11. Luminous Sources (3) Phosphorescent Light • Phosphorescence is the ability to store energy from another source of light and then emit it slowly over a long period Phosphorescent Coral • Light of one wavelength (colour) is absorbed by coral, transformed into another colour or wavelength, then emitted

  12. Luminous Sources (4) Chemiluminescence • Light produced from a chemical reaction with little or no increase in temperature • “cool light” • Very efficient • Glow sticks • Luminol

  13. Luminous Sources (5) Bioluminescence • The ability of a plant or animal to produce light • Some algae, jellyfish, insects, bacteria, and fungi can produce their own light

  14. Luminous Sources (6) Triboluminescence • Producing light from friction • Some crystals will glow simply by rubbing them together • Hitting wintergreen lifesavers with a hammer (in the dark)

  15. Luminous Sources (7) Electric Discharge • An electric current passes through air or another gas and produces light • Lightning, neon lights, and carbon-arc light

  16. Luminous Source (9) OLEDs • An organic light-emitting display (OLED) is a light source made of several extremely thin layers of organic molecules that use an electric current to produce light

  17. Luminous Sources (10) Plasma Displays • Each colour is a tiny fluorescent light in which an electrical signal causes a gas to release UV radiation • The radiation is absorbed by phosphors that radiate light in the visible spectrum • Different phosphors are used to produce red, blue, and green

  18. Luminous Sources (11) LCDs • Liquid crystal displays • A white light shines behind a liquid crystal • A liquid crystal is a solid that can change the orientation of its molecules like a liquid when electricity is applied • The crystal can block or transmit light depending on the amount of electricity applied • Red, green, and blue filters are placed in front of the crystal to produce colour

  19. Non-Luminous Sources (1) Reflecting Objects • Light from another source bounces off an objects surface • Mirrors, the moon, glass, snow, any non-black object

  20. Non-Luminous Sources (2) Refracting Objects • Light changes direction as it goes from one material to another • Prisms, lenses, rainbows, mirages, diamonds

  21. Non-Luminous Sources (3) Objects with Interference • Light rays go through each other and interact • Holograms, fibre optics, colours on oil spills and soap bubbles

  22. The End