Light production


Published on

Published in: Education, Business, Technology
1 Like
  • Be the first to comment

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide
  • Sometimes there is mercury vapour inside the glass tube (how fluorescent bulbs are made – national geographic) (how fluorescence in bulbs works, links ideas of fluorescence and electric discharge with neon tubes)
  • Sometimes there is mercury vapour inside the glass tube
  • (ABL) (THEL)
  • Answer pg 469 Q #1, 5, 9, 10
  • Light production

    1. 1. Luminous Sources
    2. 2. Light ProductionLuminous source Non-luminous source• Produces its own light • Does not produce own light• Example: sun, light bulb, lit • Seen only by using match reflected light
    3. 3. Luminous Sources• Incandescence• Electric discharge• Phosphorescence• Fluorescence• Chemiluminescence• Bioluminescence• Triboluminescence• Light-emitting diode (LED)• Laser
    4. 4. Incandescence• Production of light as a result of high temperature• Air from bulb removed and Heated tungsten filament glows replaced with non-reactive gas• Prevents filament from reacting with oxygen and bursting into flame• 5-10% of energy converted to visible light• Most converted to infrared light (heat)• Inefficient
    5. 5. Electric Dischargelight productionby passing anelectric currentthrough a gas
    6. 6. Electric Discharge• Neon lights = Geissler tubes (1855)• Vacuum pump removed most of the air from a closed tube• Remaining air glowed when an electric current passed through• Colour of glow depended on gas inside tube
    7. 7. Phosphorescence• Light production by the absorption of UV light resulting in the emission of visible light over an extended period of time• Objects coated with phosphors that absorb UV light. Phosphors keep some of the energy and over time release some of the lower energy as visible light.• Example: glow-in-the-dark
    8. 8. Fluorescence• Light production by the absorption of UV light resulting in immediate emission of visible light• Example: fluorescent dyes in detergent, highlighter pens, fluorescent lighting
    9. 9. Fluorescent LightStructure of Fluorescent Lights• Light tube filled with low-pressure mercury vapour and an inert gas (e.g. Argon)• Inner surface of tube coated with fluorescent material known as phosphorsHow Fluorescent lights work (video) Electric Discharge: Electric current causes Hg atoms to emit UV light7. Fluorescence: UV light strikes phosphors which convert the energy into visible light
    10. 10. Fluorescent LightPro Con• Same light output as • More expensive than incandescent bulb but incandescent bulbs less heat produced • Contain mercury and• Uses less electricity for should be treated like same amount of light hazardous waste for• Lasts longer disposal
    11. 11. Chemiluminescence• Production of light as the result of a chemical reaction• “Cold light”: Little to no heat is produced
    12. 12. ChemiluminescenceHow light sticks work:• One chemical in a narrow small glass vial• Other chemical in main body• Bending stick breaks glass vial• Chemical mix in the main body• Reaction produces visible light
    13. 13. Chemiluminescence Application • Camping • Law enforcement • Military personnel • Entertainment venues • Emergencies • Underwater divers (source has no moving parts, completely sealed) • Hazardous environments where a spark could be dangerous (source does not require electric current)
    14. 14. Bioluminescence• Production of light in living organisms as a result of a chemical reaction• Little to no heat produced• Function: protection from predators, lure prey, attract mates• Example: luciferase enzyme in fireflies catalyze oxidation of luciferin protein to produce light
    15. 15. AnglerFish
    16. 16. Bioluminescence• Green Fluorescent Protein (GFP): exhibits bright green fluorescence when exposed to blue light• Originally discovered in jelly fish• Now used extensively in research as a marker for gene expression
    17. 17. Triboluminescence• Production of light from friction (rubbing), pressure (crushing) or mechanical shock (scratching)• Explained by the breaking of chemical bonds in the material• Most often seen in rubbing of certain crystals• Also works with Wintergreen hard candy, pulling apart 2 pieces of duct tape, peeling transparent Scotch tape
    18. 18. Light-emitting diode (LED)• Production of light by an electric current flowing in a diode• Diode: a simple type of semiconductors• Semiconductor: a material that allows electric current to flow in only one direction• Applications: Christmas lights, traffic lights
    19. 19. Light-Emitting Diode ComparisonCompared to incandescent bulbs Compared to compact fluorescentPros bulbs• No filament (doesn’t burn out) Pros• Not much heat production (less • No toxic mercury wasted energy) • More energy efficient (longer• More energy efficient (longer lifespan, lower power usage) lifespan, lower power usage)Cons Cons• Produces a cool ‘blue’ light • Higher up-front costs instead of the warm ‘yellow’ light
    20. 20. LASER• Light• Amplication by• Stimulated• Emission of• Radiation
    21. 21. Properties of Laser LightLasers Incandescent• emit wavelengths of • emit wavelengths of the same energy level many different energy• results in a light beam levels of a single pure colour • results in white light• monochromatic (combination of all colours)
    22. 22. Properties of Laser Light• Waves are directional (travel in the same direction)• Results in light that is concentrated into one narrow beam and can travel great distances without spreading out• Waves are coherent (wave fronts launch in unison)• Results in light that is very intense
    23. 23. Application of Lasers- Manufacturing: cutting glass, burning through steel- Astronomy: measure Earth-moon distance- Research: surveyor to measure distance- Entertainment: laser light shows- Military: Boeing airborne laser, tactical high energy laser- Media technology: CD, DVD
    24. 24. Military Application of Lasers Airborne Laser (ABL) (video)
    25. 25. Military Application of LasersTactical HighEnergy Laser(THEL) (video)
    26. 26. Media Technology Application• CD & DVDs are read by lasers• Pits: bumps on discs that scatter laser light in all directions• Land: non-bumps that reflect laser light• Reflected light is converted into binary code (0’s and 1’s)
    27. 27. DVD & Blu-Ray Construction DVD Blu-RayLaser Red BlueWavelength 650 nm 405 nmPit 0.4 µm 0.15 µmTrack pitch 0.74 µm 0.32 µmStorage 4.7 GB 25 GB
    28. 28.