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Lecture 14 - Refraction (Ch. 25.4-25.5)

# Lecture 14 - Refraction (Ch. 25.4-25.5) - Lecture 14...

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Unformatted text preview: Lecture 14 Reflection and Refraction of Light The Ray Model of light o The ray model is a useful simplification for describing how light waves travel o A “ray” is a line perpendicular to the wavefronts (crests) of the wave The diagram shows a traveling plane wave and the corresponding rays Validity of the Ray Model o We can model light (or sound) as traveling in straight lines (“geometric optics”) as long as it only encounters boundaries whose size is much larger than the wavelength Otherwise diffraction occurs (Chapter 27) Specular Reflection o In reflection from a smooth surface, parallel rays are reflected in parallel Necessary for image formation by reflection Surface variations must be small compared to wavelength Metals, still water and other “shiny” surfaces The Law of Reflection o A light ray is reflected at the angle of incidence Incoming angle equals outgoing angle Angles are always measured from a normal to the surface Incoming and outgoing ray in the same plane with normal to surface o In diffuse reflection, the normal is the local normal (of a bump) θ 1 = θ 1 ′ Ange of Reflection Equals the Angle of Incidence Law of Reflection Law of Reflection Example Problem: What is theta? Law of Reflection Example Problem: What is theta? 90 - 35 = 55 65 25 35 90 - 65 = 25 180 - 120 - 25 = 35 55 Light at a Boundary o At a boundary between two different media, light can be both reflected and transmitted o The proportion of light reflected vs. transmitted depends on the angle and the optical properties of the media Light at a Boundary o Light “bends” when refracted into new material....
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Lecture 14 - Refraction (Ch. 25.4-25.5) - Lecture 14...

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