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Announcements 11/8/10

Announcements 11/8/10. Prayer Exam 2 graded: median score 79 (after 2 pt curve) Found PpP book Still missing slinkies from: Stephen Grant Ty Beus Jon Mortensen Chris Read Roger Brown Tess Larson (I think she dropped; does anyone know her?). Quick writing.

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Announcements 11/8/10

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  1. Announcements 11/8/10 • Prayer • Exam 2 graded: median score 79 (after 2 pt curve) • Found PpP book • Still missing slinkies from: • Stephen Grant • Ty Beus • Jon Mortensen • Chris Read • Roger Brown • Tess Larson (I think she dropped; does anyone know her?)

  2. Quick writing • Draw the ray diagram for this situation: Converging lens, f = 20 cm, p = 80 cm

  3. Quick writing • Draw the ray diagram for this other situation: Converging lens, f = 20 cm, p = 15 cm

  4. Quick writing • Draw the ray diagram for this third situation: Diverging lens, f = -20 cm, p = 5 cm

  5. Reading Quiz • What’s the term used to refer to rays failing to focus because a lens is shaped incorrectly? • elliptical aberration • hyperbolic aberration • parabolic aberration • spherical aberration

  6. Spherical Aberration Credit: the next several slides were produced by Dr. Durfee

  7. Reducing Spherical Aberration with Aperture

  8. Spherical Aberration

  9. Reducing Spherical Aberration by Reversing Lens

  10. Coma

  11. 0 Degree Tilt

  12. 10 Degree Tilt

  13. 20 Degree Tilt

  14. 30 Degree Tilt

  15. 40 Degree Tilt

  16. 40 Degree Tilt + Aperture

  17. Lens-makers’ eqn: Thought question • Red light coming from O produces an image at I. Where will blue light coming from O form an image? • same place • closer to the lens • farther from lens ChromaticAberration

  18. How does a camera work? • Simplest picture • What if you leave out the lens? • What’s a pinhole camera?

  19. Reading Quiz • What is the f-number of a lens? • The focal length in meters • The focal length in inches • One over the focal length in meters • The focal length divided by the diameter of the lens • The focal length divided by 25 cm

  20. q Thought question • How does the f-number of a lens relate to the half-angle of the “light cone” formed by parallel light entering the lens?

  21. Cameras: f-stops • Which has the higher f-number? • What’s the advantage of one over the other?

  22. Thought question • If you have trouble seeing things far away but can see close objects well, you are “near-sighted”. What kind of lenses do you need in your glasses? • Converging lenses • Diverging lenses

  23. Near point vs. Far point • Near point: how close can you see things comfortably • Regular person: np  25 cm • Farsighted person: np = much larger • Far point: how far away can you focus on things • Regular person: fp = infinity • Nearsighted person: fp = much smaller • For me, my fp  1 m (right eye), 0.5 m (left eye)

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