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(Page 199)

10.1. (Page 199). 10.1 Sources and Nature of Light. 10.1. Types of Light. Light sources can be natural ___________or artificial ___________. For all light sources, atoms must absorb ___________ and electrons become excited – When atoms relax they release this energy as _________________.

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(Page 199)

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  1. 10.1 (Page 199) 10.1 Sources and Nature of Light

  2. 10.1 Types of Light • Light sources can be natural ___________or artificial ___________ • For all light sources, atoms must absorb ___________ and electrons become excited – When atoms relax they release this energy as _________________

  3. 10.1 Light From the Sun • Fusion reactions involving hydrogen atoms occurs in the sun (_______________) • Huge amounts of energy are released during fusion; excited atoms on outer layer of sun release energy as ______________________

  4. 10.1 Light From Incandescence • Incandescence: __________________________________ • In a light bulb, electrical energy causes the atoms within the tungsten wire to get very hot and ____________ • Very inefficient! ____________________________________

  5. 10.1 Light from Electric Discharge • Streetlights are yellowish since the light is emitted from a heated gas - ______________________ • Most streetlights are ______________________________ • An electric current is passed through sodium gas causing the electrons in the atoms to get excited, when they relax __________________ light is given off

  6. 10.1 Fluorescence • A fluorescent bulb is filled with argon and mercury (Hg) gas • The inside of the tube is coated with _________________ • Electrical energy causes the release of electrons which excite the Hg gas • Hg gas release UV light; the UV light excites the phosphor which releases visible light

  7. 10.1 Efficiency of Fluorescence • A fluorescent bulb is 20% efficient (_____________________________________________) • Fluorescent bulbs last longer than ______________ bulbs

  8. 10.1 Uses of fluorescent light

  9. 10.1 Types of Luminescence Luminescence: Light produced by a material that has not been heated (e.g. ___________________________________ _____________________________________) Phosphorescence: Light that is emitted due to exposure of the source to UV light and continues to be emitted for minutes or hours

  10. 10.1 Types of Luminescence Chemiluminescence: Light that is produced by a chemical reaction _________________in temperature

  11. 10.1 Types of Luminescence Bioluminescence: Light that is produced by a biochemical reaction in a _______________________

  12. 10.1 • Take a minute and read page 408 of the textbook……. Then do questions # 1-4 on page 407

  13. 10.1 The Nature of Light • Light is the only form of energy that can travel through empty space and through some materials • Light behaves as an electromagnetic wave and involves the movement of energy from one point to another • Electromagnetic waves are invisible and can travel through a vacuum at the speed of light (3 x 108 m/s)

  14. 10.1 The Nature of Light • Scientists compare electromagnetic waves to water; however electromagnetic waves involve electric and magnetic fields • Wavelength: The distance from one crest (or trough) of a wave to the next crest (or trough)

  15. 10.1 The Electromagnetic Spectrum • The electromagnetic spectrum: A diagram that shows the range of electromagnetic waves arranged in the order of wavelength or frequency

  16. Do questions #1, 2, 3, 4, 5 and 7 on page 410

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