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Chapter 14

Chapter 14 . Section 1: refraction. Objectives. Recognize situations in which refraction will occur. Identify which direction light will bend when it passes from one medium to another. Solve problems using Snell’s law. Refraction of light.

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Chapter 14

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  1. Chapter 14 Section 1: refraction

  2. Objectives • Recognize situations in which refraction will occur. • Identify which direction light will bend when it passes from one medium to another. • Solve problems using Snell’s law.

  3. Refraction of light • The bending of light as it travels from one medium to another is call refraction. • As a light ray travels from one medium into another medium where its speed is different, the light ray will change its direction unless it travels along the normal. • Frequency remains constant. • Velocity changes as a result of wavelength change. • Simulations • http://www.walter-fendt.de/ph14e/refraction.htm ******* • http://www3.interscience.wiley.com:8100/legacy/college/halliday/0471320005/simulations6e/index.htm

  4. refraction

  5. Refraction of light • Refraction can be explained in terms of the wave model of light. • The speed of light in a vacuum, c, is an important constant used by physicists. • Inside of other mediums, such as air, glass, or water, the speed of light is different and is usually less than c.

  6. refraction Less Rigid Medium More Rigid Medium Refracted ray bends towards the normal.

  7. Angle of refraction • The angle between the refracted ray and the normal

  8. Law of refraction • An important property of substances is the index of refraction • Theindex of refractionfor a substance is the ratio of the speed of light in a vacuum to the speed of light in that substance.

  9. Indices of Refraction for Various Substances

  10. indices Vacuum 1.00 Air 1.0003 Water 1.33 Ethanol 1.36 Crown glass 1.52 Quartz 1.52 Diamond 2.42

  11. Law of refraction • When light passes from a medium with a smaller index of refraction to one with a larger index of refraction (like from air to glass), the ray bends toward the normal. • When light passes from a medium with a larger index of refraction to one with a smaller index of refraction (like from glass to air), the ray bends away from the normal. • Note:The speed of light has a lower speed in a more optically dense medium

  12. example • What is the speed of light in quartz? • Answer: 1.97 x 10 8 m/s

  13. Law of refraction • Objects appear to be in different positions due to refraction. • Snell’s Law determines the angle of refraction

  14. Snell’s law Snell’s Law A light ray of wavelength 589 nm (produced by a sodium lamp) traveling through air strikes a smooth, flat slab of crown glass at an angle of 30.0º to the normal. Find the angle of refraction, r.

  15. solution Snell’s Law Given:i = 30.0º ni = 1.00 nr = 1.52 Unknown: r = ? Use the equation for Snell’s law.

  16. video Lets watch some videos

  17. Student guided practice • Do problems 1-3 in your book page 487

  18. Homework • Do worksheet

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