Download Constructing the image from a plane mirror I

Chapter 34
Geometric Optics
PowerPoint® Lectures for
University Physics, Twelfth Edition
– Hugh D. Young and Roger A. Freedman
Lectures by James Pazun
Copyright © 2008 Pearson Education Inc., publishing as Pearson Addison-Wesley
Objects, images, and light rays
• Light rays from a source will radiate
in all directions, reflect from mirrored
surfaces, and bend if they pass from a
material of one index to another.
• Consider Figures 34.1, 34.2, and 34.3.
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Constructing the image from a plane mirror I
• Following the light rays to
form an image of an object.
• Consider Figure 34.4.
• Consider Figure 34.5.
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Constructing the image from a plane mirror II
• Consider Figure 34.6, below left.
• Consider Figure 34.7, below right. Images from a plane mirror show
left/right reversal.
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Reflections from a spherical mirror
•
Images from a concave mirror change depending on the object position.
Consider Figure 34.10.
•
Concave and convex mirror sign convention. Consider Figure 34.11.
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Sign convention
What is sign of image distance and radius of
curvature?
A. s’ > 0, R > 0
B. s’ > 0, R < 0
C. s’ < 0, R > 0
D. s’ < 0, R < 0
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Sign convention
What is sign of image distance and radius of
curvature?
A. s’ > 0, R > 0
B. s’ > 0, R < 0
C. s’ < 0, R > 0
D. s’ < 0, R < 0
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The focal point and focal length of a spherical mirror
• The focal point is at half of the mirror’s radius of curvature.
• All incoming rays will converge at the focal point.
• Consider Figure 34.13.
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Q34.1
Which of the following changes its focal length
when it is immersed in water?
A. a concave mirror
B. a convex mirror
C. a diverging lens
D. all of the above
E. none of the above
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A34.1
Which of the following changes its focal length
when it is immersed in water?
A. a concave mirror
B. a convex mirror
C. a diverging lens
D. all of the above
E. none of the above
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Q34.2
A concave mirror with a radius of curvature of 20 cm
has a focal length of
A. 40 cm.
B. 20 cm.
C. 10 cm.
D. 5 cm.
E. answer depends on the index of refraction
of the air around the mirror
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A34.2
A concave mirror with a radius of curvature of 20 cm
has a focal length of
A. 40 cm.
B. 20 cm.
C. 10 cm.
D. 5 cm.
E. answer depends on the index of refraction
of the air around the mirror
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A system of rays may be constructed to reveal the image
•
Rays are drawn with regard to the object, the optical axis, the focal
point, and the center of curvature to locate the image.
•
Consider Figure 34.14 to view one such construct.
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The convex spherical mirror I
• If you imagine standing inside a shiny metal ball to visualize the
concave spherical mirror, imagine standing on the outside to
visualize the concave spherical mirror.
• Consider Figure 34.16 to introduce the convex spherical mirror.
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A graphical method for mirrors
• On slide 11, we hinted at a graphical formalism using the object,
the center of curvature, the focal point, and the mirror plane.
• Consider Figure 34.19 to view the entire formalism.
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Thin lenses I
• The converging
lens is shown in
Figure 34.28.
Note symmetrical
focal points on
either side of the
lens.
• Figure 34.29 uses
the same ray
formalism as we
used with mirrors
to find the image.
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Thin lenses II
•
Figure 34.31 at bottom left illustrates a diverging lens scattering light rays and
the position of its second (virtual) focal point.
•
Figure 34.32 illustrates some assorted common arrangements of lens surfaces.
•
Follow Example 34.8.
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Q34.8
An object PQ is placed
in front of a converging
lens, forming a real
image P´Q´. If you use
black paint to cover the
lower half of the lens,
A. only the object’s upper half will be visible in the image.
B. only the object’s lower half will be visible in the image.
C. only the object’s left-hand half will be visible in the image.
D. only the object’s right-hand half will be visible in the image.
E. the entire object will be visible in the image.
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A34.8
An object PQ is placed
in front of a converging
lens, forming a real
image P´Q´. If you use
black paint to cover the
lower half of the lens,
A. only the object’s upper half will be visible in the image.
B. only the object’s lower half will be visible in the image.
C. only the object’s left-hand half will be visible in the image.
D. only the object’s right-hand half will be visible in the image.
E. the entire object will be visible in the image.
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Graphical methods for lenses
•
Figure 34.36 applies to lenses the same ray-tracing method we used for
mirrors.
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Magnifying lens
A magnifying lens with focal length 15cm is used
to magnify an ant which is 10 cm away.
• Draw a ray diagram of this situation
• Calculate the distance the image is away from
the lens
• How big does the 2 mm long ant appear?
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The camera
• A clever
arrangement of
optics with a
method to record
the inverted image
on its focal plane
(sometimes film,
sometimes an
electronic
array, it depends
on your camera).
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The eye—vision problems
•
When the lens of the eye
allows incoming light to
focus in front of or behind
the plane of the retina, a
person’s vision will not be
sharp.
•
Figure 34.45 (at right) shows
normal, myopic, and
hyperopic eyesight.
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Vision correction—examples
•
Follow Example 34.13, illustrated in Figure 34.49 in the middle of the
page.
•
Follow Example 34.14, illustrated in Figure 34.50 at the bottom of the
page.
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The microscope
•
Optical elements are arranged to magnify tiny images for visual
inspection. Figure 34.52 presents the elements of an optical
microscope.
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The astronomical telescope
•
Optical elements are arranged to magnify distant objects for visual
inspection. Figure 34.53 presents the elements of an astronomical
telescope.
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The reflecting telescope
•
Optical elements are arranged to reflect collected light back to an
eyepiece or detector. This design eliminates aberrations more likely
when using lenses. It also allows for greater magnification. The
reflective telescope is shown in Figure 34.54.
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