1. Announcements 11/5/12 Prayer
Term project progress reports due Saturday night
Slinkies: Ryan & Clement
Frank & Ernest

2. From warmup
Extra time on?
(nothing in particular)
Other comments?

3. Class-designed problem
Lens 1: f = _____
Distance to Lens 2 = _____
Lens 2: f = _____
Ray diagram? (for first lens)
Final q = ? Real or virtual?
Mtot = ? Upright or inverted?
5 mins for class to solve

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

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

6. Quick writing
Draw the ray diagram for this third situation: Diverging lens, f = -20 cm, p = 15 cm

7. Aberrations

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

9. Reducing Spherical Aberration with Aperture

10. Spherical Aberration

11. Reducing Spherical Aberration by Reversing Lens

12. Coma

13. 0 Degree Tilt

14. 10 Degree Tilt

15. 20 Degree Tilt

16. 30 Degree Tilt

17. 40 Degree Tilt

18. 40 Degree Tilt + Aperture

19. Clicker question: Chromatic Aberration
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
Lens-makers’ eqn:

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

21. From warmup
If the camera is initially focused on a distant object, to focus on a close object , must the lens be moved away from the CCD or moved toward the CCD?
Away from the CCD, because since the focal length of the lens is constant, if p gets smaller, q must get bigger.

22. F-number
f# = The focal length divided by the diameter of the lens

23. Clicker 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? q

24. From warmup
Suppose you are comparing two cameras which both use the same size sensor and the same zoom level. One of them gives the aperture specification as "f/2.8" whereas the other one is "f/2.2". Which one allows more light to reach the sensor? (Or do they allow the same?)
f/2.2, because it increases the area of aperture
That depends on how long the shutter is open for each one. The one with f/2.2 will let more light through in a given time, but if the shutter speeds are timed differently, then in a single picture they may let the same amount of light through, or either one may have more.

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

26. Clicker 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

27. Near point vs. Far point
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)
Near point: how close can you see things comfortably
Regular person: np  25 cm
Farsighted person: np = much larger
How to fix things with glasses?
Nearsighted: object at  cm  image at –fp (diverging lens)
Farsighted: object at 25 cm  image at –np (converging lens)