Announcements 11/8/10

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# Announcements 11/8/10 - PowerPoint PPT Presentation

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
• Prayer
• Exam 2 graded: median score 79 (after 2 pt curve)
• Found PpP book
• Stephen Grant
• Ty Beus
• Jon Mortensen
• Roger Brown
• Tess Larson (I think she dropped; does anyone know her?)
Quick writing
• Draw the ray diagram for this situation: Converging lens, f = 20 cm, p = 80 cm
Quick writing
• Draw the ray diagram for this other situation: Converging lens, f = 20 cm, p = 15 cm
Quick writing
• Draw the ray diagram for this third situation: Diverging lens, f = -20 cm, p = 5 cm
• 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
Spherical Aberration

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

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

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

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