MIRROR
E QUA T I O N
Objectives
a. Define Mirror Equation
b. Derive and use the mirror equation in
predicting the characteristics and
position of an image formed by mirrors
c. Solve problems involving Mirror
Equation
Q1. Can you give me an example of a
fraction?
Q2. How do you add fr actions? Try
this!
Q3. If you will have this equation and
you are asked to derive a formula for
letter b, how are you going to do that?
The Mirror Equation can be used to provide numerical
information and predict characteristics of image formed by
curved mirrors. Quantitatively, it showsrelationship between
the object distance (do), the image distance (di) and the focal
length (f). I t is given by:
Where:
f = focal length
do = obj ect dist ance
di = image dist ance
T he r elat ionship of t he r at io of t he image dist ance (di) and
object distance (do) to the ratio of the image height (hi) and
object height (ho) is called the magnification equation. I t is
expr essed by:
Where:
M = magnification
ho = obj ect height
hi = image height
do = obj ect dist ance
di = image dist ance
MIRROR
E QUA T I O N
Q1. What is Mirror Equation?
Q2. How can we express Mirror Equation?
Q3. How can we express the magnification
equation?
Let’s try this!
Who am I? What am I?
Ex ample
Problem
1: A 3.0 cm tall light bulb is placed at a distance of
32 cm from a convex mirror having a focal length
of -10.2cm. Determine the image distance and the
image size.
Given:
ho = 3.0 cm
do = 32 cm
f = -10.2 cm
find:
di = ?
hi =?
Given:
ho = 5.00 cm
do = 40 cm
f = 9 cm
find:
di = ?
hi =?
Problem #1. Determine the image distance and
image height for a 4 cm tall object placed 8 cm from
a mirror having focal length of 12 cm.
Problem #2: A mirror has a focal length of -8.8 cm.
An object which is 7cm tall is placed 30.00 cm from
the mirror’s surface. Determine the image distance
and image height.
Illustrate each problem then describe the
characteristics of the image for each problem.
Remember!
You can apply Mirror Equation to both concave and
convex mirrors.
The concave mirror creates different images if an
object is placed in different positions, while the
convex mirror has one set of characteristics of the
image formed; always virtual image or behind the
mirror, upright, and reduced in size.
P O S TT E S T
Direction: Solve this problem and write your
answer in a ½ length wise.
A 5 cm pencil is placed 20 cm in front
of a convex mirror whose focal
length is -20 cm. Find:
a. image distance from the mirror
b. height of the image produced.
AGREEMENT
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tch?v=um4boWdSWnw&t=5s
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F or Today !
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