Announcements 11/8/10
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Transcript 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:
a. Stephen Grant
b. Ty Beus
c. Jon Mortensen
d. Chris Read
e. Roger Brown
f. 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
Reading Quiz
What’s the term used to refer to rays failing to
focus because a lens is shaped incorrectly?
a. elliptical aberration
b. hyperbolic aberration
c. parabolic aberration
d. spherical aberration
Spherical Aberration
Credit: the next several slides were produced by Dr. Durfee
Reducing Spherical Aberration with
Aperture
Spherical Aberration
Reducing Spherical Aberration by
Reversing Lens
Coma
0 Degree Tilt
10 Degree Tilt
20 Degree Tilt
30 Degree Tilt
40 Degree Tilt
40 Degree Tilt + Aperture
Thought question
Chromatic Aberration
Red light coming from O produces an image at I.
Where will blue light coming from O form an
image?
Lens-makers’ eqn:
a. same place
1
1
1
b. closer to the lens
n 1
f
R1 R2
c. farther from lens
How does a camera work?
Simplest picture
What if you leave out the lens?
What’s a pinhole camera?
Reading Quiz
What is the f-number of a lens?
a. The focal length in meters
b. The focal length in inches
c. One over the focal length in meters
d. The focal length divided by the diameter of
the lens
e. The focal length divided by 25 cm
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?
1
1
a. q 2cos
f-number
b. q sin 1 f-number
1
f-number
c. q sin 1
1
d. q tan f-number
1
1
e. q tan
2
f-number
q
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 “nearsighted”. What kind of lenses do you need in
your glasses?
a. Converging lenses
b. Diverging lenses
Near point vs. Far point
Near point: how close can you see things
comfortably
a. Regular person: np 25 cm
b. Farsighted person: np = much larger
Far point: how far away can you focus on
things
a. Regular person: fp = infinity
b. Nearsighted person: fp = much smaller
– For me, my fp 1 m (right eye), 0.5 m (left
eye)