Physics 123 23. Light: Geometric Optics 23.1 The Ray Model of Light 23.2 Reflection - Plane Mirror 23.3 Spherical Mirrors 23.5 Refraction - Snell’s law

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Text of Physics 123 23. Light: Geometric Optics 23.1 The Ray Model of Light 23.2 Reflection - Plane Mirror...

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  • Physics 123
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  • 23. Light: Geometric Optics 23.1 The Ray Model of Light 23.2 Reflection - Plane Mirror 23.3 Spherical Mirrors 23.5 Refraction - Snells law 23.7 Converging and Diverging Lenses
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  • Reflection ii rr i = r Angle of incidence equals the angle of reflection
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  • Image in a Plane Mirror
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  • d o = d i
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  • Spherical Mirrors Concave mirror Convex mirror
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  • Concave Mirror radius = r focus = f r f f = r / 2
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  • Concave Mirror A parallel ray reflects through the focus
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  • Concave Mirror Solar Cooker!
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  • Concave Mirror A ray through the focus reflects parallel
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  • Concave Mirror Image is inverted, real, reduced
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  • Concave Mirror Equation 1 / d o + 1 / d i = 1 / f
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  • Concave Mirror Problem A 3 cm high candle is located 5 cm from a concave mirror whose radius of curvature is 20 cm. What are the characteristics of the image?
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  • Concave Mirror Problem f = 10 cm 1/d o + 1/ d i = 1/f 1/5 + 1/ d i = 1/10 1/ d i = - 1/10 d i = - 10 cm The image is 10 cm behind the mirror, virtual, upright, and magnified 2X m = - d i / d o
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  • Concave Mirror Problem Makeup mirror! If the object is within the focus of the concave mirror the image is enlarged (magnified), upright but virtual its all in your head!!!
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  • Convex Mirror
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  • Image will ALWAYS be reduced, virtual, upright
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  • Jurassic Park! Rear View Mirror Objects in the mirror are closer than they appear!
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  • Convex Mirror Equation 1 / d o + 1 / d i = 1 / f Note: f is negative d i is negative
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  • Convex Mirror Problem A 3 cm high candle is located 5 cm from a convex mirror whose radius of curvature is 20 cm. What are the characteristics of the image?
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  • Convex Mirror Problem f = - 10 cm 1/d o + 1/ d i = 1/f 1/5 + 1/ d i = - 1/10 1/ d i = - 3/10 d i = - 3.3 cm The image is 3.3 cm behind the mirror, virtual, upright, and reduced in size m = - d i / d o m = 1 / 3
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  • Refraction ii rr
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  • Index of Refraction n = sin i / sin r
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  • Refraction Problem The index of refraction of glass is 1.5. A ray of light is incident on a glass pane at an angle of 60 0. Calculate the angle of refraction.
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  • Refraction Problem n = sin i / sin r 1.5 = sin 60 0 / sin r 1.5 = 0.866 / sin r sin r = 0.866 / 1.5 sin r = 0.58 r = 35 0
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  • Converging (convex) Lens
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  • Converging Lens When the object is outside the focus, the image is real and inverted
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  • Converging Lens When the object is inside the focus, the image is virtual, upright, and enlarged.
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  • Diverging (concave) Lens
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  • The image is ALWAYS reduced, upright, virtual
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  • Lens Problem A 35 mm slide projector uses a converging lens with f = 20 cm. The screen is 3 m away. How far is the slide from the lens?
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  • Lens Problem 1/d o + 1/ d i = 1/f 1/d o + 1/ 300 = 1/20 1/d o = 1/20 - 1/ 300 d o = 21. 4 cm m = - d i / d o m = - 300 / 21.4 m = -14 Image is real, inverted, magnified
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  • Thats all folks!