Textbook Reference 10.3 (P.419-430)
Learning Goals
 Understand how to draw ray diagrams for concave
mirrors
 Be able to identify when images are real or virtual
Success Criteria
 To draw at least one ray diagram for concave
mirrors and to identify if the image is real or
virtual.
Curved Mirrors
 Mirrors with a single curvature find
many uses in our homes and optical
devices. To make a curved mirror,
you must make part of the surface of
the sphere reflective. There are two
types of curved mirrors:
 Concave (converging)
 Convex (diverging).
Types of Curved Mirrors
1. Concave (Converging) Mirror:
• Shaped like part of the surface of a sphere in
which the inner surface is reflective.
• For example, similar to the surface of a bowl.
2. Convex (Diverging) Mirror:
• Shaped like part of the surface of a sphere in
which the outer surface is reflective.
Concave Mirror
Terminology
 Centre of Curvature:
 The centre of the sphere whose surface has been used to make the mirror.
Its the point at which the normals meet. Labelled C.
 Principal Axis:
 The line through the centre of curvature to the midpoint of the mirror.
 Vertex:
 The point where the principal axis meets the mirror. Labelled V.
 Focus or Focal Point:
 The point at which light rays parallel to the principal axis converge (meet at
a common point) when they are reflected off a concave mirror. Labelled F.
Concave Mirrors
Light comes
from this side
Vertex
Centre of
Curvature (C)
Principle
Axis (PA)
Focal length
Focus (F)
Locating Images in Concave Mirrors
 To determine the image of an
object in front of a concave
mirror, you need to draw at least
two incident rays from the top of
the object.
RULES:
 1. A light ray parallel to the
principal axis is reflected through
the focus.
Locating Images in
Concave Mirrors
RULES ... Cont`d:
 2. A light ray through the centre
of curvature is reflected back into
itself.
 3. A ray through the focus will
reflect parallel to the principal
axis.
 4. A ray aimed at the vertex will
follow through the law of
reflection.
EXAMPLE ... FIND THE IMAGE
Recall what a REAL IMAGE is ...
A Real Image is an image that can be seen on a
paper screen as a result of light rays actually
arriving at the image location.
Real Image:
 Formed when reflected rays (not extended rays)
meet
 Located in the front of the mirror
 You need a screen to see the real image
EXAMPLE ... FIND THE IMAGE
SALT
... SIZE (smaller, larger,
or same), ATTITUDE
(upright or inverted),
LOCATION, and TYPE
(real or virtual)
SALT ...
SIZE = Larger
ATTITUDE = Inverted
LOCATION = Beyond C
TYPE = Real
JIGSAW
There are 5 scenarios to investigate with Concave mirrors.
You will be placed in groups and assigned a scenario to
work on, during which time you will become the `expert`
on that scenario.
Afterwards, everyone will JIGSAW into another group
where you will all have a turn to `teach` your new group
members about your concave mirror scenario.
Please reference your textbook (p.422-424) during this
activity.
JIGSAW GROUPS
GROUP 1
Adoma
Annamaria
Helder
Vanessa
David
Stephen
GROUP 2
Julia
Anthony
Stephanie
Jonathan
Abdullah
Raffaela
GROUP 3
Akin
Victor
Michael
Alissia
Higor
Rachel
GROUP 4
Haya
Andre
Ivo
Josie
Matthew
GROUP 5
Angelica
Alex
Cristian
Gabriel
Sevak
Victoria
SUMMARY: IMAGING PROPERTIES
OF A CONVERGING MIRROR
OBJECT
LOCATION
Beyond C
At C
Between C
and F
At F
Between F
and mirror
IMAGE CHARACTERISTICS
SIZE
ATTITUDE
(smaller, larger, or same)
(inverted or upright)
LOCATION
TYPE
(Real or virtual)
SUMMARY: IMAGING PROPERTIES
OF A CONVERGING MIRROR
OBJECT
LOCATION
Beyond C
At C
Between C
and F
IMAGE CHARACTERISTICS
SIZE
ATTITUDE
(smaller, larger, or same)
(inverted or upright)
SMALLER
INVERTED
BETWEEN C &
F
REAL
SAME
INVERTED
AT C
REAL
LARGER
INVERTED
BEYOND C
REAL
At F
Between F
and mirror
LOCATION
TYPE
(Real or virtual)
NO CLEAR IMAGE
LARGER
UPRIGHT
BEHIND
MIRROR
VIRTUAL
The following 5 slides are for reference
purposes.
Case 1: The object is located beyond C
- When an object is located beyond C, the image will always be located
between C and the Focus.
- The image will be inverted.
- The image is reduced in size.
- The image is real.
Case 2: The object is located at C
- When an object is located at C, the image will also be located C.
- The image will be inverted.
- The image is the same size.
- The image is real.
Case 3: The object is located between C and F
- When an object is located between C and F, the image will be located
beyond C.
- The image is inverted.
- The image is larger.
- The image is real.
Case 4: The object is located at F
- When the object is located at F, there is no image formed. WHY
- Light rays from the same point do not converge. Reflected rays are
parallel and do not form images.
Case 5: The object is located in front of F
(between F and the mirror)
- When an object is located between F
and the mirror, the image will always
be located somewhere on the
opposite side of the mirror.
- The image is upright.
- The image is larger.
- The image is virtual. This is because
the rays diverge and our brain
extrapolates the rays backwards to
where they appear to originate.