# Mirrors and lenses

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21-Jan-2015Category

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### Transcript of Mirrors and lenses

- 1. Ch 18Mirrors and Lenses

2. Plane Mirror flat, smooth surface thatreflects light in a regularway; it produces an image thatis virtual, erect, and thesame size as the object; left and right appear tobe interchanged, butfront and back areinterchanged 3. Types of Images Real image - source of converging light rays; canbe projected; are always inverted Virtual image - source of diverging light rays;cannot be projected; are always erect 4. Concave Mirror reflects light off its inner surface Focal point - (f) point on the principle axis wherereflecting light converges; f equals one-half the radius of curvature (C) 5. Spherical Aberration defect of all spherical mirrors when the parallel raysdont all reflect through the focal point; correct this by using a parabolic mirror 6. Concave Mirror Characteristics If the object is outside C, the image is real, inverted, and smaller 7. Concave Mirror Characteristics If the object is at C, the image is real, inverted, and the same size 8. Concave Mirror Characteristics If the object is between C and f, the image is real, inverted, and larger 9. Concave Mirror Characteristics If the object is inside f, the image is virtual, erect, and larger 10. Mirror Equation 1 = 1 + 1 or di = f x dof do dido f f is the focal length do is the object distance di is the image distance magnification - the ratio of the image size (hi) to theobject size (ho) m = hi = - di ho do 11. Mirror Equation Rules di is positive for real images, negative for virtualimages hi is positive for erect images, negative forinverted images f is positive for concave mirrors, negative forconvex mirrors 12. Convex mirror reflects light off the outer surface images are always virtual, erect, and smaller these are used as safety mirrors because you get a wider angle of vision 13. Lens transparent material with a refractive indexlarger than air The focal length of the lens depends on theshape and refractive index of the material 14. Convex Lens Convex lens - (converging lens) thicker in themiddle than at the edges; acts like a concavemirror. Chromatic aberration - caused when light passesthru the edge of a lens; the light is dispersed;correct using an achromatic lens 15. Convex Lens Characteristics Outside 2f, image is real,inverted, and smaller 16. Convex Lens Characteristics At 2f, image is real,inverted, and same size 17. Convex Lens Characteristics Between 2f and f, imageis real, inverted, andlarger 18. Convex Lens Characteristics Inside f, image is virtual,erect, and larger 19. Concave lens (diverging lens) thinnerin the middle than at theedgesacts like a convexmirror. Always produces virtual,erect, and smaller image 20. Lens Equation Rules The equation and rules stay the same except f ispositive for convex lens and negative forconcave lens 21. Corrective Lenses 22. Near-Sighted People have too short a focal length correct this using a concave (diverging) lens 23. Far-Sighted People have too long a focal length, correct this using a convex (converging) lens