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Chapter 17 Reflection and Refraction

Chapter 17 Reflection and Refraction. Objectives. 17.1 Explain the law of reflection 17.1 Distinguish between diffuse and specular reflection 17.1 Calculate the index of refraction in a medium. Objectives. 17.2 Explain total internal reflection 17.2 Define the critical angle

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Chapter 17 Reflection and Refraction

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  1. Chapter 17 Reflection and Refraction

  2. Objectives • 17.1Explain the law of reflection • 17.1 Distinguish between diffuse and specularreflection • 17.1 Calculate the index of refraction in a medium

  3. Objectives • 17.2Explain total internal reflection • 17.2 Define the critical angle • 17.2 Explain effects caused by the refraction of light in a medium with varying refractive indices • 17.2 Explain dispersion of light in terms of the index of refraction

  4. Reflection • Specular: Mirror • Diffuse: Everything else

  5. What is Smooth? • Are the molecular gaps smaller than the wavelength? Than specular reflection • Basketball is larger than gaps, so specular reflection occurs • Metals: Due to sea of electrons, form sort of a flatness (like flowing water) • Are the molecular gaps larger than the wavelength? Than diffuse reflection • Most objects tend to have much larger gaps than 400 – 700 nm

  6. In the House Application • Mirrors are coated with Silver or Aluminum • Silver is better (99 – 92), not every color equal • Two reflections, one from glass, one from back • Silver reflects 99 RG and 97 B • Aluminum 92 RG and 90 B

  7. Refraction

  8. Snells Law • How much refraction? Depends on speed of light through material • n is speed of light where 1 is true speed • Larger than 1 means slowed down (2 means half as fast

  9. What is the index of Refraction • If a light from a vacuum runs into water at 30 degrees, what is the angle of the light traveling in the water. N value of 1 for vacuum, 1.33 for water • N values • Vacuum 1.00 • Air 1.0003 • Water 1.33 • Ethanol 1.36 • Crown Glass 1.52 • Quartz 1.61 • Diamond 2.42

  10. Total Internal Reflection • When all light reflects due to a large angle (critical angle) • Looking into distance water = large angle = critical angle = total reflection

  11. Total Internal Reflection • Optic Fibers use this principal

  12. Mirages • Refraction of light through air (different densities)

  13. Sunrise and Sunset • Sun actually not where it appears to be

  14. Going Fishing

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