A World of Light and Color
Activity 10
Image Formation from a Curved Mirror
Procedure and Results Sheet (No Prediction Sheet)
Key Questions:


How are images formed in curved mirrors?
Can we predict the location, size, and type of image formed in curved mirrors?
Materials:



Pencil (1)
Ruler (1)
White paper (several)
Procedure: Part 1 — Flat Mirror
1. This first exercise is to help you review how images are formed flat mirrors. Below is a
chess pieces placed in front of a mirror. Draw three rays from the tip of the arrow and trace
the reflected rays. Use a ruler. Make sure you follow the law of reflection—counting
squares and looking for symmetry in the incident and reflected rays will help. Follow the
reflected rays back through the mirror using dotted lines. Repeat this process for three rays
coming from the bottom of the arrow. Draw the image of the chess piece.
2. Does the object distance equal the image distance?
YES
NO
3. What is a virtual image? Is the image you have drawn a virtual image? You may find the
discussion on pages 53-54 of your textbook helpful in answering this question.
10.1
Part 2 — Convex Mirror
1. In the mirror shown below, mark the center (C ) , the focal point F and the vertex (V ) with
dots. The vertex V is in the middle of the curved surface of the mirror, and the center C is
located 12 blocks to the right of V.
How many blocks long is the radius of curvature (R ) of the spherical mirror? _____
The focal point (F ) of the mirror located 6 blocks to the right of the vertex. How many
blocks long is the focal length (f ) of the spherical mirror? _____
Write an equation relating f and R
_________________
2. A line that contains the vertex, center, and focal point is called the optical axis. Draw and
label the optical axis on the diagram below.
3. Rays that are near the optical axis are called paraxial rays. There are three special paraxial
rays called principal rays.
Principal rays
 An incident ray that is parallel to the optical axis reflects as if it is originating from the
focal point.
 An incident ray that moves towards the center reflects back on itself.
 An incident ray that moves towards the focal point reflects parallel to the optical axis.
The first incident ray that is parallel to the optical axis is already shown below.
Draw all three principal rays below and their corresponding reflected rays.
10.2
4. Use the ray tracing rules to locate the image of the chess piece. If the rays do not seem to
converge to the same point (but seem to diverge instead), extrapolate the rays to form an
image. Notice that we only need to draw two of the principal rays in order to find the image
of any point; you can choose any 2 of the 3 principal rays discussed above.
Draw two rays from the top of the chess piece, then find their intersection point. This will be
the image of the top of the chess piece.
Repeat for two rays from the bottom of the chess piece.
5. Answer the following questions.
(a) Is the image reduced or magnified? ____________
(b) Is the image upright or inverted? ____________
(c) What is the magnification? ____________
1 1 1
 
d o di f
object distance is do
Mirror equation
Magnification equation m 
d
imageheight
 i
objectheight
do
image distance is di
6. Verify that the mirror and magnification equations are valid by using numbers from your
picture.
10.3
7. Now consider a situation where the chess piece is located above the optical axis of the
mirror.
Draw at least two rays from the top of the chess piece to locate the top of the image.
Draw at least two rays from the bottom of the chess piece to locate the bottom of the image.
Connect the top and bottom points of the image.
What do you notice about your image?
8. Now consider a situation where the chess piece is located below the optical axis of the
mirror.What do you notice about your image?
Part 3 — Concave Mirror
10.4
1. In the CONCAVE mirror shown below, mark the center (C ) , the focal point F and the
vertex (V ) with dots. The vertex V is in the middle of the curved surface of the mirror, and
the center C is located 12 blocks to the LEFT of V.
How many blocks long is the radius of curvature (R ) of the spherical mirror? _____
The focal point (F ) of the mirror located 6 blocks to the LEFT of the vertex. How many
blocks long is the focal length (f ) of the spherical mirror? _____
Write an equation relating f and R
_________________
2. A line that contains the vertex, center, and focal point is called the optical axis. Draw and
label the optical axis on the diagram below.
3. Rays that are near the optical axis are called paraxial rays. There are three special paraxial
rays called principal rays.
Principal rays
 An incident ray that is parallel to the optical axis reflects as if it is originating from the
focal point.
 An incident ray that moves towards the center reflects back on itself.
 An incident ray that moves towards the focal point reflects parallel to the optical axis.
The first incident ray that is parallel to the optical axis is already shown below.
Draw all three principal rays below and their corresponding reflected rays.
10.5
9. Use the ray tracing rules to locate the image of the chess piece below. If the rays do not seem
to converge to the same point (but seem to diverge instead), extrapolate the rays to form an
image.
Draw two rays from the top of the chess piece, then find their intersection point. This will be
the image of the top of the chess piece.
Repeat for two rays from the bottom of the chess piece.
10. Answer the following questions.
Is the image reduced or magnified? ____________
Is the image upright or inverted? ____________
What is the magnification? ____________
1 1 1
 
d o di f
object distance is do
Mirror equation
Magnification equation m 
d
imageheight
 i
objectheight
do
image distance is di
11. Verify that the mirror and magnification equations are valid by using numbers from your
picture.
10.6
12. Now consider a situation where the chess piece is located above the optical axis of the
mirror.
Draw at least two rays from the top of the chess piece to locate the top of the image.
Draw at least two rays from the bottom of the chess piece to locate the bottom of the image.
Connect the top and bottom points of the image.
What do you notice about your image?
13. Now consider a situation where the chess piece is located below the optical axis of the
mirror. What do you notice about your image?
10.7