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Chapter 19
Optical Instruments
Topics:
• The thin-lens equation
• The camera
• The human eye
• The magnifier
• The microscope
• The telescope
• Resolution of optical
instruments
Sample question:
This anablepsis is called the “four-eyed fish.” How must the top
half of its eye differ from the lower half so that it has clear vision
both above and below the waterline at the same time?
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Slide 19-1
Reading Quiz
1. The units of refractive power are
A. watts.
B. m2.
C. m–1.
D. joules.
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Slide 19-2
Answer
1. The units of refractive power are
D. joules.
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Slide 19-3
Reading Quiz
2. Accommodation of the eye refers to its ability to
A. focus on both nearby and distant objects.
B. move in the eye socket to look in different directions.
C. see on both the brightest days and in the dimmest light.
D. see both in air and while under water
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Slide 19-4
Answer
2. Accommodation of the eye refers to its ability to
D. see both in air and while under water
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Slide 19-5
Reading Quiz
3. The magnification of a microscope is increased when
A. the focal length of the objective lens is increased.
B. the focal length of the objective lens is decreased.
C. the focal length of the eyepiece is increased.
D. the distance between the objective lens and eyepiece is
decreased.
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Slide 19-6
Answer
3. The magnification of a microscope is increased when
C. the focal length of the eyepiece is increased.
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Slide 19-7
Reading Quiz
4. The fundamental resolution of an optical instrument is set by
A. the accuracy to which lenses can be polished.
B. the fact that white light is composed of all visible colors.
C. the fact that all types of glass have nearly the same index
of refraction.
D. the wave nature of light.
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Slide 19-8
Answer
4. The fundamental resolution of an optical instrument is set by
D. the wave nature of light.
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Slide 19-9
The Thin-Lens Equation
1 1 1
 
s s f
Thin-lens equation (also works for mirrors)
relating object and image distance to focal length
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Slide 19-10
Sign Conventions for Lenses and Mirrors
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Slide 19-11
The Camera
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Slide 19-12
Focusing a Camera
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Slide 19-13
Digital Cameras
A digital image is made up
of millions of pixels.
A CCD chip records the
digital image.
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Slide 19-14
The Human Eye
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Slide 19-15
Focusing and Accommodation
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Slide 19-16
Myopia and Hyperopia
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Slide 19-17
Correcting Myopia
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Slide 19-18
Apparent Size
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Slide 19-19
The Magnifier
Largest angular size
without a magnifier is
h
0 
25 cm
With a magnifier,
the angular size is
h
0 
f
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The magnification is thus
 25 cm
M

0
f
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The Microscope
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Slide 19-21
The Microscope
L 25 cm
M  MoMe  
f0 fe
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Slide 19-22
The Telescope
f0
M 
fe
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Slide 19-23
Lens Aberrations: Spherical Aberration
The Hubble space
telescope originally
suffered from
spherical aberration.
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Slide 19-24
Chromatic Aberration
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Slide 19-25
Resolution and the Wave Nature of Light
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Slide 19-26
Rayleigh’s Criterion
Two objects are resolvable if their
angular separation is greater than
1.22 
1 
D
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Slide 19-27
The Resolution of a Microscope
Numerical aperture NA  nsin 0
Resolving power RP  dmin
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0.610

NA
Slide 19-28
Optical and Electron Micrographs of e. coli
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Slide 19-29