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Unformatted text preview: Curved Mirrors Almost any operation that can be performed with a lens can also be performed with a curved mirror. Because light passes through the lens but bounces off the mirror, concave mirrors produce converging rays with positive focal lengths, and convex mirrors cause ray divergence and have negative focal lengths. Notice, too, that a positive focal length is now to the left of the lens and a negative f is to the right. Object and image distances must also be positive to the left because since the rays bounce off the mirror rather than passing through a lens. An ideal shape for focusing parallel rays would be a parabolic reflector , but there is no universally best shape for all situations, so spherical surfaces will be used again. Since there is now only one radius of curvature to keep track of and no index of refraction, the focal length is simply f = r/2 where the r is negative if the reflecting surface is convex....
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 Spring '11
 Tibbets
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