Mirror Equation
chapter 13
lesson 5
Objective
you will be able to use the mirror equations to
describe the size, distance and nature of the
image produced.
Concave Mirrors
Concave mirrors bend inward (like a cave).
The images produced are real, inverted and diminished
if the object is beyond the focal point.
Virtual, erect and enlarged if between the focal point
and the vertex
Convex Mirrors
Convex mirrors curve outward and the images
produced are virtual, erect and diminished
Equation for Height
As we saw in our exercise, the height of the object(ho),
the height of the image(hi), the distance away from the
mirror the object is (do) and the distance from the mirror
the image forms (di) are related by the ratios
Sign Conventions
Images formed on the same side as the object are real
and have positive distances.
Virtual images are behind the mirror and have negative
distances.
Upright (erect) images are positive and inverted are
negative.
Mirror Equation
example
A 4.00-cm tall pencil is placed a distance of 45.7 cm
from a concave mirror having a focal length of 15.2 cm.
Determine the image distance
image size.
Describe the image.
example
A 4.00-cm tall pencil is placed a distance of 8.3 cm
from a concave mirror having a focal length of 15.2 cm.
Determine the image distance
image size
Describe the image
Assignment
Read p. 661-665
Do SNAP p. 180-4 all
Answers to even
2: 3.5 cm 4: no image 6: 0.33
8: 4.8 cm 10: m=2.5, concave
12: 1.7 cm