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WHAT IS LIGHT?

WHAT IS LIGHT?. INTRODUCTION. What does optics mean?. Physical properties of light. Light and Colour. Why does bright lights seem to make things more vivid at night?. U2 360 Tour. How can white light allow us to see objects with so much colour? Why is the sky blue?. Reasons:.

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WHAT IS LIGHT?

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  1. WHAT IS LIGHT? INTRODUCTION

  2. What does optics mean? Physical properties of light

  3. Light and Colour • Why does bright lights seem to make things more vivid at night?

  4. U2 360 Tour

  5. How can white light allow us to see objects with so much colour? Why is the sky blue?

  6. Reasons: • White light contains all of the colours of the rainbow. • The sky is blue because the particles like water vapour in the air reflect the colour blue and absorb all the other colours found in white light

  7. Sources of Light

  8. 1) Natural Sources of Light

  9. SUN! • most important natural source of light

  10. Other Stars

  11. Lightning

  12. Fires

  13. Bioluminescence • ability of organisms to produce light • 90 % of all sea creatures can • in very deep water no light reaches • use light to see prey • scare predators • camouflage • some produce their own • some contain bacteria that produce light

  14. angler fish • long spine with a bulb • used as a lure to attract prey

  15. Jellyfish • use light to attract fish into their tentacles

  16. Flashlight fish • use light to help to keep in a school

  17. Fireflies • attract mates by chemical reactions

  18. 2) Artificial Light

  19. Incandescent Light • produced by metals at very high temperatures • bulbs contain a filament or thin wire (tungsten) • uses electricity to heat up • filament emits light as a way to release some energy as a glow

  20. Fluorescent Light • bulb such as gas such as mercury vapour • mercury vapour is exposed to electricity which emits UV light • bulb is coated with a white powder called phosphor • phosphor glows after exposed to UV radiation

  21. Compact Fluorescent Bulbs • even though compact fluorescent lights are more efficient than incandescent light bulbs, still 80% of energy is converted into heat

  22. Phosphorescent Light • ability to store energy from radiation • different from fluorescent since phosphor needs UV light • phosphorescent materials glow in the dark for some time after being energized by light • glow in the dark will fade but can re-energize with a light source

  23. Chemiluminescence • light produced from chemical reactions (no heat or temperature change) • “cool light” • bioluminescence are also forms • ex. luminol used in forensics: glows when it reacts to iron in blood • ex. glow sticks

  24. How Glow Sticks Work

  25. Triboluminescence • light producing from friction • rubbing crystals together • quartz used in rattles in Aboriginal people flashes light • breaking crystals or rubbing diamonds

  26. Electric Discharge • produce light using electric current through air or another gas • halogen gases used often • ex. carbon-arc involves passing a current through the air between 2 rods

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