Classical Photography

1
The Geometric Optics of Image Formation
2
(I) Clear Materials Bend Rays Light bending is
called "refraction".
ray
Air
Water
where a straight ray would come from.
where the ray really comes from.
3
Refraction
The amount of bending depends on a property of
the material called "index of refraction", n.
Water n is low
Glass n is high
4
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum
Vacuum V 300,000,000 m/s
5
Refraction
wavefronts
Vacuum V 300,000,000 m/s
6
Refraction
wavefronts separated by one wavelength
Vacuum V 300,000,000 m/s
7
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
8
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
9
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
10
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
11
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
12
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
13
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
14
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
15
Index of refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s Velocity
in other media is less than c Medium velocity
vacuum 3 x 108 m/s air 2.999 x 108
m/s water 2.26 x 108 m/s glass 2 x
108 m/s diamond 1.25 x 108 m/s
16
Index of refraction
The index of refraction, n, of a medium is
defined as the ratio of the speed of light in a
vacuum to the speed in that mediumn
c/v Medium velocity n vacuum 3 x 108
m/s 1 air 2.999 x 108 m/s 1.0003 water
2.26 x 108 m/s 1.33 glass 2 x 108
m/s 1.5 diamond 1.25 x 108 m/s 2.4
17
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
Glass V 200,000,000 m/s
18
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
Glass V 200,000,000 m/s
19
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
Glass V 200,000,000 m/s
20
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
Glass V 200,000,000 m/s
21
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
Glass V 200,000,000 m/s
22
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
Glass V 200,000,000 m/s
23
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
Glass V 200,000,000 m/s
24
Refraction
The velocity of light in a vacuum is a
fundamental constant c 3 x 108 m/s
Vacuum V 300,000,000 m/s
Glass V 200,000,000 m/s
25
Vacuum V 300,000,000 m/s
Glass V 200,000,000 m/s
26
Refraction for Different Materials
light
45?
AIR
WATER
GLASS
DIAMOND
32?
28?
16?
27
Snells Law n1sin?1 n2sin?2 Examples
Material Index of Refraction, n Vacuum 1
(exactly) Air 1.0003 (approximately 1.000)
Water 1.33 Glass 1.5 Diamond 2.4
28
Snells Law The equations
Snells Law n1sin?1 n2sin?2
Define n 1 for a vacuum All other values of n
are gt1.
29
Snells Law n1sin?1 n2sin?2 It works exactly
the same in reverse.
Material 1
?1
n1
n2
?2
Material 2
Material Index of Refraction, n Vacuum 1
(exactly) Air 1.0003 (approximately 1.000)
Water 1.33 Glass 1.5 Diamond 2.4
30
Into and out of a flat plate of glass.
Glass n2 1.5
Air, n1 1.00
Air, n3 1.00
q4
q3
n3sin?3 n4sin?4
n1sin?1 n2sin?2
q2
q1
31
It can be shown that
q1 q4
q2 q3
and the input and output rays are parallel.
Glass n2 1.5
Air, n1 1.00
Air, n3 1.00
q4
q3
q2
q1
32
Using Refraction to Focus Light.
n11
n11
Glass Lens in Air
Parallel Rays
n21.5
Focal point of lens
Optical Axis
Focal length of lens, f
33
Parallel rays come to focus at one pointon the
image plane.
n11
n11
Glass Lens in Air
n21.5
Optical Axis
Parallel Rays different direction
Image Plane
Focal length of lens, f
34
A Chief Ray is a ray heading towardor away from
the center of the lens.
n11
n11
Glass Lens in Air
Examples of Chief Rays
n21.5
Optical Axis
Focal length of lens, f
35
Thin Lens ApproximationChief Rays pass through
the lens without deviation.
n11
n11
Glass Lens in Air
Examples of Chief Rays
n21.5
Optical Axis
Focal length of lens, f