UNIT 8
Light and Optics
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Monday February 20th
Light and Optics
2
TODAY’S AGENDA
Monday, February 20
 Curved Mirrors Convex
 Hw: Practice C (even) p466
UPCOMING…
 Tue:
Problem Quiz #1
Color and Polarization
 Wed: Refraction
 Thurs: Thin Lenses Biconvex Lens
 Fri:
Thin Lenses Biconcave Lens
 Mon: Total Internal Reflection
3
Chapter 13
Light and Reflection
Formation of Images by Spherical Mirrors
Spherical mirrors are shaped like sections of a sphere, and
may be reflective on either the inside (concave) or outside
(convex).
Formation of Images by Spherical Mirrors
Using geometry, we find that the focal length is half the radius of
curvature:
Formation of Images by Spherical Mirrors
We use ray diagrams to determine where an image will be.
For mirrors, we use three key rays, all of which begin on
the object:
1. A ray parallel to the principal axis; after reflection it
appears to come from the focal point.
2. A ray lines up with the focal point; after reflection it is
parallel to the principal axis and appears to come from
a position parallel behind the mirror.
3. A ray to the center of the mirror; after reflection it is the
same angle to the principal axis. The principal axis
bisects the reflected angle. The ray appears to come
from behind the mirror.
Images Formed by Spherical Mirrors
Convex Mirror
Images Formed by Spherical Mirrors
Convex Mirror
do
-di
-f
Images Formed by Spherical Mirrors
Image Characteristics
Type:
Size:
Orientation:
Real or Virtual
Larger, Smaller, or Same (as the Object)
Upright or Inverted
do :
always positive
di:
real is positive; virtual is negative
f:
in front of mirror is positive; Behind mirror is negative
Images Formed by Spherical Mirrors
*Remember: for Convex mirrors, focal length is negative
and distance of the image is negative.
Chapter 23 Mirrors and Lenses
If you stand in front of a convex mirror, at the same
distance from it as its radius of curvature,
(A) you won't see your image because there is none.
(B) you will see your image at your same height.
(C) you will see your image and you will appear smaller.
(D) you will see your image and you will appear larger.
Images Formed by Spherical Mirrors (Problem)
The image of a distant tree is virtual and very small when
viewed in a curved mirror. The image appears to be 18 cm
behind the mirror. What kind of mirror is it, and what is its
radius of curvature?
Chapter 23 Mirrors and Lenses
A single convex spherical mirror produces an image which is
(A) always virtual.
(B) always real.
(C) real only if the object distance is less than f.
(D) real only if the object distance is greater than f.
Images Formed by Spherical Mirrors
Magnification
Convex
Mirror
M > 1 Larger
M < 1 Smaller
M = 1 Same
M + Upright
M - Inverted
do
-di
-f
hi
di
M=

ho
do
*Remember: for Convex mirrors, focal
length is negative and distance of the
image is negative.
Images Formed by Spherical Mirrors
END
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