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Optics

Optics. The Study of Light. Areas of Optics. Geometric Optics Light as a ray. Physical Optics Light as a wave. Quantum Optics Light as a particle. Optical images. Nature real (converging rays) virtual (diverging rays) Orientation upright inverted Size true enlarged reduced.

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Optics

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  1. Optics The Study of Light

  2. Areas of Optics • Geometric Optics • Light as a ray. • Physical Optics • Light as a wave. • Quantum Optics • Light as a particle.

  3. Optical images • Nature • real (converging rays) • virtual (diverging rays) • Orientation • upright • inverted • Size • true • enlarged • reduced

  4. Law of Reflection • Angle of incidence equals angle of reflection. r i

  5. + - Image -5 cm Plane Mirror object 5 cm

  6. shiny shiny Spherical mirrors - + - + (where reflected rays go) (dark side) (where reflected rays go) (dark side) concave convex Focal length, f, is negative Focal length, f, is positive

  7. Focus Parts of aSpherical Concave Mirror - + Vertex Center Principle axis

  8. C F Spherical Concave Mirror(object outside center) c p Real, Inverted, Reduced Image f

  9. C F Spherical Concave Mirror(object at center) Real, Inverted, True Image

  10. C F Spherical Concave Mirror(object between center and focus) Real, Inverted, Enlarged Image

  11. C F Spherical Concave Mirror(object at focus) No image

  12. C F Spherical Concave Mirror(object inside focus) Virtual, Upright, Enlarged Image

  13. Parts of aSpherical Convex Mirror + - Principle axis Focus Center

  14. Spherical Convex Mirror F C Virtual, Upright, Reduced Image

  15. Mirror equation #1 • 1/si + 1/so =1/f • si: image distance • so: object distance • f: focal length

  16. Mirror equation # 2 • M = -si/so = hi/ho • si: image distance • so: object distance • hi: image height • ho: object height • M: magnification

  17. Concave Image is real when object is outside focus Image is virtual when object is inside focus Focal length f is positive Convex Image is always virtual Focal length f is negative Concave vs convex mirrors

  18. Real Formed by converging light rays si is positive when calculated with mirror equation Virtual Formed by diverging light rays si is negative when calculated with mirror equation Real vs Virtual images

  19. Upright Always virtual if formed by one mirror or lens hi is positive when calculated with mirror/lens equation Inverted Always real if formed by one mirror or lens hi is negative when calculated with mirror/lens equation Upright vs Inverted images

  20. Definition: Refraction Change in speed of light as it moves from one medium to another. Can cause bending of the light at the interface between media.

  21. Index of Refraction speed of light in vacuum speed of light in medium n = c/v n =

  22. angle of incidence 1 2 angle of refraction Snell’s Law n1sin 1 = n2sin 2 n1 n2

  23. 1 2 n1 < n2 light bends toward normal n1 n2

  24. 1 2 n1 > n2 light bends away from normal n1 n2

  25. Dispersion The separation of white light into colors due to different refractive indices for different wavelengths.

  26. Dispersion Due to different indices of refraction for different wavelengths of light.

  27. c r Critical Angle of Incidence n1 Light would refract 90o so it reflects instead, undergoing total internal reflection. n2 n1 > n2

  28. Calculating Critical Angle n1sin(1) = n2sin(2) n1sin(90o) = n2sin(2) n1 = n2sin(c)

  29. i r Occurs only when angle of incidence > critical angle Total Internal Reflection n1 n2

  30. Consider a lens with f = 20 cm. • You place a 5 cm tall object 30 cm in front of the lens. • Draw the ray diagram and construct the image. • Calculate the image distance and height using the lens/mirror equations. • Name the image.

  31. - + F F 2F 2F Converging lens #1 C Real, Inverted, Reduced Image

  32. - + F F 2F 2F Converging lens #2 C Real, Inverted, True Image

  33. - + F F 2F Converging lens #3 C Real, Inverted, Enlarged Image

  34. - + F F Converging lens #4 C Virtual, Upright, Enlarged Image

  35. For converging lenses • f is positive • so is positive • si is positive for real images and negative for virtual images • M is negative for real images and positive for virtual images • hi is negative for real images and positive for virtual images

  36. - + F F Diverging lens C Virtual, Upright, Reduced Image

  37. For diverging lenses • f is negative • so is positive • si is negative • M is positive and < 1 • hi is positive and < ho

  38. THIN LENSES Lensesare an essential part of telescopes, eyeglasses, cameras, microscopes and other optical instruments. A lens is usually made of glass, or transparent plastic.

  39. The two main types of lenses are convex and concave lenses. The focal length(f) of a lens depends on its shape and its index of refraction.

  40. A converging (convex) lens is thick in the center and thin at the edges. A diverging (concave) lens is thin in the center and thick at the edges.

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