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Physics – Verizon Next Step Program Vibrations and Waves Week 8 Notes - Mirrors and Lenses |
23.1)Flat Mirrors O is the position of the source Object. p is the distance from the object to mirror. I is the reflected Image of the object. q is the distance from the Image to the mirror. In flat mirrors, p=q. h = object height h' = image height M ≡ (image height)/(object height) = h'/h M is the Lateral Magnification. For flat mirrors, M is 1. 23.2) Images formed by spherical mirrors Concave Mirror - the object and image are inside the curve. C = Center of curvature V = midpoint of mirror R = Radius = distance from V to C M = h'/h = -q/p Where M is the Lateral Magnification. 1/p + 1/q = 2/R If the Object is very far from the mirror, the incoming rays are essentially parallel causing a Focal point to be created. F = Focal point f = distance from V to F f = R/2 1/p + 1/q = 1/f 23.3) Convex mirrors and sign conventions The equations for Concave mirrors apply to Convex mirrors as well. Sign Conventions p is + if the object is in front of the mirror (real) p is - if the object is behind the mirror (virtual) q is + if the image is in front of the mirror (real) q is - if the image is behind the mirror (virtual) Both f and R are + if the curvature is in front of the mirror (concave) Both f and R are - if the curvature is behind the mirror (convex) If M is positive, Image is upright If M is negative, Image is inverted. Note: In the real world, it is impossible for p to be negative for a non-refracting mirror. 23.4) Images Formed by Refraction n1 = index of refraction of material 1 n2 = index of refraction of material 2 n1/p + n2/q = (n2 - n1 )/ R M = h'/h = -(n1 q)/(n2 p) The same rules for mirrors also apply to refracting reflective surfaces. 22.5) The Law of Refraction A mirage is a classic example of naturally occurring refraction. The refraction is due to the fact the air has different indices of refraction at different temperatures. 23.6) Thin Lenses Converging Lenses - have positive focal lengths and are thickest in the middle. Diverging Lenses - have negative focal lengths and are thickest at the edges. The same equations for convex and concave mirrors apply to thin lenses. In addition: 1/f = (n-1)(1/R1 - 1/R2) Where R1 is the radius of curvature at the front of the lens and R2 is the radius of curvature at the back of the lens. HW 8: p. 781 M.C. # 1, p. 781 C.Q. #2, p. 782 #1 p. 783 #4 p. 783 #22 p. 784 #27