11.9
Images in Curved Mirrors
OVERALL EXPECTATIONS
• investigate, through inquiry, the properties of light, and predict its behaviour,
particularly with respect to reflection in plane and curved mirrors and
refraction in converging lenses
• demonstrate an understanding of various characteristics and properties of
light, particularly with respect to reflection in mirrors and reflection and
refraction in lenses
SPECIFIC EXPECTATIONS
Developing Skills of Investigation and Communication
• use appropriate terminology related to light and optics
• use an inquiry process to investigate the laws of reflection, using plane and
curved mirrors, and draw ray diagrams to summarize their findings
• predict the qualitative characteristics of images formed by plane and curved
mirrors, test their predictions through inquiry, and summarize their findings
Understanding Basic Concepts
• describe, on the basis of observation, the characteristics and positions of the
images formed by plane and curved mirrors, with the aid of ray diagrams and
algebraic equations, where appropriate
• identify ways in which the properties of mirrors and lenses (both converging
and diverging) determine their use in optical instruments
KEY CONCEPTS
• Optical devices benefit our society in many ways.
Time
45–60 min
Vocabulary
• concave (converging)
mirror
• convex (diverging) mirror
• centre of curvature
• principal axis
• vertex
• converge
• focus
• real image
• diverge
Assessment Resources
Assessment Rubric 1:
Knowledge and
Understanding
Assessment Summary 1:
Knowledge and
Understanding
Other Program Resources
BLM 0.0-4 Two-Column Table
BLM 0.0-8 Term Box
Science Perspectives 10
website www.nelson.com
/scienceperspectives/10
• Curved mirrors produce a variety of images.
EVIDENCE OF LEARNING
Related Resources
Gizmo: Ray Tracing
(Mirrors)
Look for evidence that students can
• describe the images formed by concave mirrors
• describe the images formed by convex mirrors
• understand how incident rays are used to determine whether an image is formed by
a curved mirror
SCIENCE BACKGROUND
Curved Mirrors
• Concave mirrors are also called
converging mirrors; convex mirrors are
also called diverging mirrors. This is
because concave mirrors cause parallel
light rays to converge, whereas convex
mirrors cause parallel light rays to diverge.
• Images formed in concave mirrors have
differing characteristics depending
upon the distance between the object
and the mirror.
De Pree, Christopher.
Physics Made Simple.
Broadway Books, 2005.
Science Perspectives 10
ExamView® Test Bank
Science Perspectives 10
Teacher eSource SUITE
Upgrade
Science Perspectives 10
website www.nelson.com
/scienceperspectives/10
▼
• Both concave and convex mirrors
can be thought of as portions of
spheres. Visualizing this is essential
because C, the centre of curvature,
determines the location of the
principle axis of the mirror. It is the
centre of the shape that would be
formed if the mirror were a complete
sphere.
▼
Meiani, Antonella.
Light (Experimenting
With Science). Lerner
Publications, 2002.
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• The characteristics of images formed
in convex mirrors are diminished size
(when compared to the actual object),
upright, behind the mirror, and
virtual. These characteristics do not
change no matter where the object is
located.
This distorts depth perception. Many
car mirrors carry the warning “Objects
in mirror are closer than they appear.”
The distortion occurs because the
convex mirror produces a small image,
making the object appear to be farther
away than it actually is.
• The side mirrors on cars are convex,
so their images are diminished in size.
POSSIBLE MISCONCEPTIONS
Identify
• Students may think that the image formed in a concave mirror always has the
same characteristics no matter where the object is located.
Clarify
• The characteristics of images formed by plane mirrors and convex mirrors are
always the same no matter where the object is located, but this is not true for
concave mirrors. The characteristics of the image formed by a concave mirror
vary depending on the location of the object.
Ask What They Think Now
• At the end of the section, ask, What do you need to know to determine the
characteristics of an image formed by a concave mirror? (the location of the
object in relation to the centre of curvature and the focus)
TEACHING NOTES
Engage
• To introduce the section, have students think of examples of concave and
convex mirrors that are useful in everyday life. Examples include ATM
mirrors, car mirrors, elevator mirrors, sunglasses, car headlights, flashlights,
and telescopes. For each example named, have students state why the concave
or convex mirror is more useful than a plane mirror for that application. Use
students’ responses to begin their exploration of the characteristics of images
formed by concave and convex mirrors.
Reading Tip
Relate It to Yourself
Encourage students to
write the examples that
they think of in their
notebook. Have students
share examples aloud or
trade notebooks, as this
may remind students of
examples that they had
not considered.
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Explore and Explain
• Before assigning the reading for this section, have students make a twocolumn table by drawing a line down the centre of a sheet of paper. Have
students label one side “Concave Mirrors” and the other side “Convex
Mirrors.” Alternatively, you could distribute BLM 0.0-4 Two-Column Table.
Tell students to use this table to organize facts and information as they
read the section. This table will provide a convenient location for students
to refer to as they continue to learn about mirrors, to remind them of the
characteristics of these two mirror types. At intervals, remind students to
make notes in their table.
• Use Figure 2 on page 496 to help students visualize how the location of C,
the centre of curvature, is determined. Note that it may be helpful to draw
the rest of the circle that is the cross-section of the mirror. Because the centre
of curvature is the centre of a sphere, it must be the centre of every circular
cross section of the sphere.
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• Move on to Figure 3. Emphasize that the focus, F, is located on the principal
axis, between the centre of curvature and the vertex. Ask, Why are concave
mirrors called converging mirrors? (This type of mirror causes parallel light rays
to converge.)
• Discuss with the class each of the numbered rays in Figure 5 on page 497.
Ask students to explain what is going on with each ray in their own words.
Explain that the way in which each reflected ray behaves is dependent upon
the way in which the incident ray approaches the mirror. This behaviour
depends upon whether the ray is parallel to the principal axis as it approaches
and whether the ray passes through the focus. As each ray is discussed, have
students trace the light ray that corresponds to the numbered statement.
• The imaging rules are applied in Figure 6. Emphasize that the characteristics
of the image depend on the location of the object in relation to C and F.
• Spend time explaining the difference between a real image and a virtual image
for a concave mirror. In Figure 6(a) on page 497, for example, if you held a
sheet of paper at the location on the diagram where the image appears, you
would actually see an image on the paper. Contrast this with the image in
Figure 10 on page 499, which appears behind the mirror as a virtual image
that would not show up on the sheet of paper.
• Discuss images in a converging mirror as explained on page 498. Ask, How
does a real image differ from a virtual image? (A virtual image is an image in
which light does not actually arrive at or come from the image location; a real
image is formed when light actually arrives at the image location.)
• After discussing the information on pages 498 and 499 describing how the
location of the object in relation to C and F determines the characteristics of
the image formed by a concave mirror, have students examine the summary
found in Table 1. Then have students create a Venn diagram comparing three
items. Have students use the headings shown in the sample below, which also
includes sample answers.
Object location
beyond C
smaller
between C and F
Reading Tip
Take Time with Diagrams
Tell students that one way
to enhance understanding
of diagrams is to duplicate
the diagram in a notebook.
Drawing and labelling
the diagram can lead to a
deeper understanding of
the concepts illustrated
in the diagram and can
identify concepts that are
confusing.
Writing Tip
Using Signal Words
Encourage students to pay
special attention to signal
words as they read the
Student Book. It may be
helpful to record the signal
words (including those
listed in the Writing Tip)
and their meanings in BLM
0.0-4 Two-Column Table
as a reference during any
reading they are doing.
Object location
between C and F
inverted
real
beyond C
image
formed
Writing Tip
larger
Writing Persuasive Text
upright
behind mirror
virtual
Object location inside F
• Have students examine the three imaging rules for a convex mirror on
page 500 of the Student Book. Because the imaging characteristics for a
convex mirror never change, any two of the three rules listed in the text will
always locate the image without requiring the use of a protractor.
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Stress the importance
to students of a strong
conclusion that ties
together the main idea
and key points. Readers
often remember best what
they read last, so one’s
conclusion may be what
makes the greatest impact
on the reader and has the
opportunity to be the most
persuasive part.
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• Have students visit the Nelson Science Perspectives 10 Student eSource to access
computer simulations involving curved mirrors.
• The imaging properties of concave and convex mirrors are summarized below.
Review the scenarios with the class and discuss any situations for which
students have questions of a concave mirror.
– When the object is placed beyond C of a concave mirror, the image is real,
inverted, smaller than the original object, and located between C and F.
– When the object is at C of a concave mirror, the image is real, inverted, the
same size as the original object, and located at C.
– When the object is located between C and F of a concave mirror, the image
is real, inverted, larger than the original object, and located beyond C.
– When the object is located between the concave mirror and F, the image is
virtual, upright, larger than the original object, and located at C.
• For a convex mirror, the image is always upright, smaller than the original,
and virtual regardless of the position of the object.
Extend and Assess
• Review how to locate images in concave and convex mirrors. Ask students to
explain similarities and differences in the methods for locating images in these
two types of mirrors. Ask them to describe the images formed by concave and
convex mirrors.
• Have students complete the Check Your Learning questions on page 501 of
the Student Book.
CHECK
YOUR LEARNING
Suggested Answers
1. Sample answers: Concave mirrors are used for parking lot lighting, and are found in reflecting telescopes in the
science classrooms. Convex mirrors are used in the library to provide wide angle views.
2. Light rays actually arrive at the location of a real image, so it can be formed (projected) on a screen. Light rays that
form a virtual image do not pass through or come from the image location; they just appear to.
3. The diagram should show that rays entering the mirror parallel to the principal axis are reflected through the focus.
focus (F )
4. Sample answer: Rays that are parallel to the principal axis will reflect through the focus. Rays that pass through
the focus as they head toward the mirror reflect parallel to the principal axis. Rays that pass through the centre of
curvature heading toward the mirror will reflect back upon themselves. A ray that strikes the vertex will obey the
laws of reflection.
5. My head is between the focus and the mirror.
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6. Diverging rays can only be traced back by the observer’s brain to an apparent point of origin, and thus never come
from or pass through the image location. Reflected rays from a convex mirror always diverge. Real images can only
form when reflected rays from a mirror converge.
F image
object
7. (a) This is a convex mirror.
(b) The image is located behind the mirror.
(c) This is a virtual image.
8. (a) image 5 smaller, inverted, between C and F, real
F
C
(b) image 5 same size, inverted, at C, real
C
F
(c) image 5 smaller, upright, on the other side of the mirror between the mirror and F, virtual
C
F
9. Real images are inverted, and virtual images are upright.
10. (a) Drivers can ‘see around corners’ due to the wide angle view the mirrors provide.
(b) Sample answers: right hand side-view mirror on a car, security mirrors in stores, decorations in homes.
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DIFFERENTIATED INSTRUCTION
Unit Task B ookmark
Have students discuss the
optical devices that were
described in this section.
Ask, How do these
devices apply the imaging
rules for curved mirrors?
(answers will vary) Ask
students to think about
how they could apply this
same information as they
complete the Unit E Task:
Building an Optical Device.
Ask volunteers to share
their thoughts with the
class.
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• Point out that diagrams are used to illustrate concepts throughout this
section. Visual/spatial learners will enjoy making diagrams for the class to
use. However, keep in mind that other learners may also benefit from actually
drawing the diagrams.
• Verbal/linguistic learners may benefit from writing out the four rules for
locating an image in a concave mirror (page 497) and displaying them in
class. Visual/spatial learners and artistic students can create diagrams to
accompany the rules.
• Visual/spatial learners and bodily/kinesthetic students may enjoy making
models of the diagrams using strings to represent light rays.
ENGLISH LANGUAGE LEARNERS
• Make sure that English language learners understand the four rules for
locating an image in a concave mirror (page 497). Show how each rule
corresponds to the diagram. Have students explain the rules in their own
words.
• Have students prepare a glossary of the terms introduced in this section.
Have them include each term, a short definition in their own words, and,
if applicable, a simple diagram or picture to represent the term. BLM 0.0-8
Term Box will be useful for this purpose.
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