8B - 15_Refl Refr_11.ppt

8B - 15_Refl Refr_11.ppt - Ray(Geometrical Optics Behavior...

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Unformatted text preview: Ray (Geometrical) Optics Behavior of light interacting with materials, ignoring the wave nature of light. But wave properties are needed to explain the index of refraction. Except for luminous bodies (Sun, lamps, fire..) we see only reflected light. Reflection is either specular (mirror) or diffuse (almost everything else). Usually, real objects send light from each of their points in all directions (diffuse). Examples: light from projector is diffusely reflected from screen bathroom mirror - you don’t see the mirror, you see yourself (specular). When mirror is fogged, you see the ‘mirror’ (diffuse). What Do We See? Law of Reflection: Θ 1 = Θ ’ 1 The “ray” is normal to the wave front (wave crest line) = direction of Poynting vector. Plane of incidence passes through the ray and is perpendicular to the surface. Can be explained by Huygens’ Principle. 1 refers to incident medium, prime refers to after hitting surface. Diffuse reflection Law of Reflection at each surface, but surfaces are irregular. Light goes in all directions randomly. Refraction and reflection Refraction of light - speed changes Index of refraction, n, describes speed of light, v , in a medium. n depends on the material and the frequency. f is constant, λ changes n - various materials at one frequency Gases have low density of molecules and n ≈ 1. Most liquids and solids have n ≈ 1.5 IN THE VISIBLE part of the EM spectrum. It can vary widely with frequency; we will study this important effect later. Refraction Law of refraction: A refracted ray lies in the plane of incidence and has an angle of refraction θ 2 that is related to the angle of incidence θ 1 by The index of refraction of a material, n, is equal to c / v , where v is the speed of light in that material and c is its speed in vacuum....
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This note was uploaded on 04/10/2011 for the course PHYS 8B taught by Professor Catherinebordel during the Spring '10 term at Berkeley.

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8B - 15_Refl Refr_11.ppt - Ray(Geometrical Optics Behavior...

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