Chapter 19
Optical
Instruments
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PowerPoint® Lectures for
College Physics: A Strategic Approach, Second Edition
19 Optical Instruments
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Slide 19-2
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.
© 2010 Pearson Education, Inc.
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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The Camera
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Focusing a Camera
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The Human Eye
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The Human Eye
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Where does most of the focusing occur?
A. The cornea
B. Aqueous Humor
C. Iris
D. Lens
E. Vitreous Humor
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Where does most of the focusing occur?
A. The cornea
B. Aqueous Humor
C. Iris
D. Lens
E. Vitreous Humor
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Where does accommodation occur?
A. The cornea
B. Aqueous Humor
C. Iris
D. Lens
E. Vitreous Humor
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Where does accommodation occur?
A. The cornea
B. Aqueous Humor
C. Iris
D. Lens
E. Vitreous Humor
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Accommodation of the eye refers to its ability to
focus on both nearby and distant objects.
Fine tuning
Near Point the closest distance an eye can focus
clearly
Far Point the farthest distance an eye can focus clearly
Ideal: Near Point: 25 cm
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Far Point: 
Hyperopia
Farsighted
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Myopia
Nearsighted
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Refractive Power
Measured in Diopters (1/meters)
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Hyperopia
Farsighted
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Virtual Image with a Converging Lens
What are the conditions that a virtual image will be
formed by a converging lens?
A. Object is far from the lens
B. Object is at the focal point of the lens
C. Object is closer to the lens than the focal point
D. Any condition
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Virtual Image with a Converging Lens
What are the conditions that a virtual image will be
formed by a converging lens?
A. Object is far from the lens
B. Object is at the focal point of the lens
C. Object is closer to the lens than the focal point
D. Any condition
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Virtual Image with a Converging Lens
What are the conditions that a virtual image will be
formed by a converging lens?
Object is closer to the lens than the focal point
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Hyperopia
Farsighted
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Myopia
Nearsighted
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A person has a far point of 50 meters and a near point
of 1 meter.
1. Are they farsighted or nearsighted?
2. Do they need a converging lens or a diverging lens?
3. Find the prescription for the appropriate corrective
lens.
a. What is the object distance, what is the image
distance?
b. Use the thin lens-equation to find the focal point
of the appropriate lens.
c. Find the power of this lens.
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1. Farsighted (they can see far just fine but not close
enough)
2. Converging Lens
3. a. s = 25 cm = 0.25 m s’ = -1 m (want to see objects
25 cm or further but can
only handle 1 meter or
more.)
b. f = 0.333 m
c. P = 3 D
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A person has a far point of 1 meter and a near point of
10 centimeters.
1. Are they farsighted or nearsighted?
2. Do they need a converging lens or a diverging lens?
3. Find the prescription for the appropriate corrective
lens.
a. What is the object distance, what is the image
distance?
b. Use the thin lens-equation to find the focal point
of the appropriate lens.
c. Find the power of this lens.
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1. Nearsighted (they can see very close but objects
beyond their reach are out of focus)
2. Diverging Lens
3. a. s = 
b. f = -1 m
c. P = -1 D
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s’ = -1 m
(want to see infinitely
far but can only handle
up to 1 meter away)