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© 2010 Pearson Education, Inc. Slide 18-2
18 Ray Optics
© 2010 Pearson Education, Inc. Slide 18-3
© 2010 Pearson Education, Inc. Slide 18-4
© 2010 Pearson Education, Inc.
The Ray Model of Light
Light rays can cross.A light ray travels forever unless it interacts with matter.
An object is a source of light rays. The eye sees by focusing a bundle of rays.
Light rays travel in straight lines.
Slide 18-9
© 2010 Pearson Education, Inc.
Sources of Light Rays: Self-Luminous ObjectsA ray source A point source
An extended source A parallel-ray source
Slide 18-10
© 2010 Pearson Education, Inc.
Seeing Objects
Seeing a ray source
Seeing an object by scattered light
Seeing a point or extended source
Slide 18-11
© 2010 Pearson Education, Inc.
Shadows
Slide 18-12
© 2010 Pearson Education, Inc.
The Law of Reflection
1. The incident ray and the reflected ray are both in the same plane, which is perpendicular to the surface, and
2. The angle of reflection equals the angle of incidence: θr = θi .
Slide 18-15
© 2010 Pearson Education, Inc.
The Plane Mirror
Slide 18-16
© 2010 Pearson Education, Inc.
Refraction
Slide 18-17
© 2010 Pearson Education, Inc.
Snell’s Law of Refraction
Slide 18-18
© 2010 Pearson Education, Inc. Slide 18-19
© 2010 Pearson Education, Inc.
Total Internal Reflection
Slide 18-21
© 2010 Pearson Education, Inc.
Locating a Virtual Image
Slide 18-22
© 2010 Pearson Education, Inc.
Thin Lenses and Ray Tracing
The focal point of a converging lens
The focal point of a diverging lens
Slide 18-23
© 2010 Pearson Education, Inc.
Three Important Sets of Rays: Converging Lenses
Slide 18-24
© 2010 Pearson Education, Inc.
Ray Tracing: Real Images
Slide 18-25
© 2010 Pearson Education, Inc. Slide 18-26
© 2010 Pearson Education, Inc.
Magnification of a Lens or Mirror
Slide 18-29
© 2010 Pearson Education, Inc.
Ray Tracing: Virtual Images
Slide 18-30
© 2010 Pearson Education, Inc.
Three Important Sets of Rays: Diverging Lenses
Slide 18-31
© 2010 Pearson Education, Inc. Slide 18-32
© 2010 Pearson Education, Inc.
Spherical Mirrors and Ray Tracing
The focal point of a concave mirror
The focal point of a convex mirror
Slide 18-35
© 2010 Pearson Education, Inc.
Three Sets of Special Rays for a Concave Mirror
Slide 18-36
© 2010 Pearson Education, Inc.
A Real Image Formed by a Concave Mirror
Slide 18-37
© 2010 Pearson Education, Inc. Slide 18-38
© 2010 Pearson Education, Inc.
Three Sets of Special Rays for a Convex Mirror
Slide 18-39
© 2010 Pearson Education, Inc.
Ray Tracing for a Convex Mirror
Slide 18-40
© 2010 Pearson Education, Inc. Slide 18-41
© 2010 Pearson Education, Inc.
The Thin-Lens Equation
Slide 18-42
© 2010 Pearson Education, Inc. Slide 18-43
© 2010 Pearson Education, Inc.
Summary
Slide 18-44
© 2010 Pearson Education, Inc.
Reading Quiz1. When an object like a tree is illuminated by the sun, and you
are looking toward the tree, light rays leave the object
A. only from points at the top and base of the tree, but in every direction.
B. from every point on the surface of the tree, but only toward your eyes.
C. only from points at the top and base of the tree, but only toward your eyes
D. from every point on the surface of the tree and in every direction.
Slide 18-5
© 2010 Pearson Education, Inc.
Answer 1. When an object like a tree is illuminated by the sun, and you
are looking toward the tree, light rays leave the object
A. only from points at the top and base of the tree, but in every direction.
B. from every point on the surface of the tree, but only toward your eyes.
C. only from points at the top and base of the tree, but only toward your eyes
D. from every point on the surface of the tree and in every direction.
Slide 18-6
© 2010 Pearson Education, Inc.
Reading Quiz2. A light ray can change direction when going from one
material into another. This phenomenon is known as
A. reflection.
B. absorption.
C. refraction.
D. scattering.
Slide 18-7
© 2010 Pearson Education, Inc.
Answer 2. A light ray can change direction when going from one
material into another. This phenomenon is known as
A. reflection.
B. absorption.
C. refraction.
D. scattering.
Slide 18-8
© 2010 Pearson Education, Inc.
If the aperture is very small, how far apart on the screen built into the left side of the box are the images of the point-like red and green light sources?
Example Problem
Slide 18-13
© 2010 Pearson Education, Inc.
If the aperture is a circle 1 cm in diameter, what are the size and shape of the image of the green point-like light source? Do you need to know how far below the center of the aperture that source is?
Example Problem
Slide 18-14
© 2010 Pearson Education, Inc.
What is the index of refraction of the plastic if a ray is refracted as in the figure?
Example Problem
Slide 18-20
© 2010 Pearson Education, Inc.
Which of these ray diagrams is possibly correct?
Checking Understanding
Slide 18-27
© 2010 Pearson Education, Inc.
Which of these ray diagrams is possibly correct?
Answer
D
Slide 18-28
© 2010 Pearson Education, Inc.
Checking UnderstandingIn this figure the image is produced by a lens. At which position A–E is the lens?
Slide 18-33
© 2010 Pearson Education, Inc.
In this figure the image is produced by a lens. At which position A–E is the lens?
Answer
D
Slide 18-34