11.1
What Is Light?
OVERALL EXPECTATIONS
• demonstrate scientific investigation skills in the four areas of skills
• identify and describe a variety of careers related to the fields of science
under study, and identify scientists, including Canadians, who have made
contributions to those fields
• evaluate the effectiveness of technological devices and procedures to make use
of light, and assess their social benefits
• 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
Scientific Investigation Skills
• formulate scientific questions about observed relationships, ideas, problems,
and/or issues, make predictions, and/or formulate hypotheses to focus
inquiries or research
• conduct inquiries, controlling some variables, adapting or extending
procedures as required, and using standard equipment and materials safely,
accurately, and effectively, to collect observations and data
Career Exploration
• identify scientists, including Canadians, who have made a contribution to the
fields of science under study
Relating Science to Technology, Society, and the Environment
• analyze a technological device that uses properties of light and explain how it
has enhanced society
Developing Skills of Investigation and Communication
• use appropriate terminology related to light and optics
Understanding Basic Concepts
• identify and label the visible and invisible regions of the electromagnetic
spectrum
• describe properties of light, and use them to explain naturally occurring
optical phenomena
Time
45–60 min
Vocabulary
• medium
• radiation
• electromagnetic wave
• visible light
• electromagnetic spectrum
• visible spectrum
Skills
Researching
Analyzing the issue
Communicating
Evaluating
Predicting
Observing
Analyzing
Equipment and Materials
per group:
• ray box
• two triangular prisms
• sheet of white paper
Assessment Resources
Assessment Rubric 1:
Knowledge and
Understanding
Assessment Summary 1:
Knowledge and
Understanding
Other Program Resources
BLM 11.1-1 Try This: Can
Colours Be Split?
Skills Handbook 1. Safe
Science
Skills Handbook 4. Research
Skills
Science Perspectives 10
website www.nelson.com
/scienceperspectives/10
KEY CONCEPTS
• Optical devices benefit our society in many ways.
• Light is an electromagnetic wave that travels at high speed in a straight line.
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EVIDENCE OF LEARNING
Related Resources
Gizmo: Basic Prism
Look for evidence that students can
Kirkland, Kyle, Ph. D and
Sean M. Grady. Optics:
Illuminating the Power
of Light. Facts on File,
2006.
• identify scientists who have contributed to the understanding of the nature of light
• describe ways that electromagnetic waves are used in technological devices and are
utilized in society
• identify and label the parts of the electromagnetic spectrum
• describe the properties of light
Science Perspectives 10
ExamView® Test Bank
Science Perspectives 10
Teacher eSource SUITE
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SCIENCE BACKGROUND
Science Perspectives 10
website www.nelson.com
/scienceperspectives/10
The Nature of Light
• The speed of light in a vacuum is
299 792 459 m/s, often rounded
to 300 000 000 m/s. This speed
applies not only to light waves,
but to all forms of electromagnetic
(EM) radiation, from radio waves to
gamma rays. The different forms of
electromagnetic radiation differ in their
wavelength, frequency, and energy.
• Wavelength of visible light is typically
measured in nanometres (nm). One
nm 5 1 3 1029 m. Visible light falls
in the range of about 380 to 750 nm
(3.8 3 1027 to 7.5 3 1027 m). Light
outside this range (for example UV
light) is not visible to the human eye.
• Not all EM radiation is microscopic.
The radio waves that are used by
televisions and cellular phones, for
example, can range from 1 cm to 1 m
in length.
• The frequency of light is directly
proportional to the amount of energy
it carries. Wavelength is inversely
proportional to frequency: the greater
the wavelength the lower the energy
light has. High frequency, shortwavelength ultraviolet light is highenergy radiation. Long-wavelength,
low-frequency radio waves are low in
energy. While high-energy radiation
such as UV light, X-rays, and gamma
rays have uses that help people,
in general, high-energy radiation
also has greater potential danger to
people than low-energy radiation.
The harmful of effects of exposure
to high-energy radiation range
from sunburn to increased risk of
developing cancer.
• Earth’s atmosphere protects our planet
from many forms of EM radiation.
Visible light can pass through, as can
some UV rays and radio waves. UV
rays that pass though the atmosphere
can cause sunburn.
• Examining other parts of the EM
spectrum (other than visible light)
provides information about the
Universe that cannot be obtained by
focusing only on visible light.
POSSIBLE MISCONCEPTIONS
Identify
• When students hear the term radiation, they may think exclusively of nuclear
radiation, which is harmful to humans.
Clarify
• Radiation refers to all energy that is transmitted at the speed of light and that
does not require a medium for transmission. All forms of electromagnetic
waves are transferred through radiation. There are two broad categories of
radiation: ionizing and non-ionizing. Non-ionizing radiation, such as visible
light and radio waves, does not carry enough energy to change atoms and
molecules by removing electrons. Ionizing radiation, on the other hand, has
enough energy to change atoms and molecules. Gamma rays and X-rays are
examples of ionizing radiation that are harmful to life.
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Ask What They Think Now
Ask, Is
• all radiation harmful to humans? Students should express an understanding
of the term radiation as referring to energy transmission and understand that
only some forms of radiation, such as X-rays and gamma rays, are harmful.
TEACHING NOTES
Engage
• Engage students’ interest by briefly shutting off the classroom lights. Turn the
lights back on, and explain to students that visible light is just one part of the
electromagnetic spectrum. Initiate a discussion of ways humans rely on visible
light. Have students write down and discuss facts they know about visible light,
and have volunteers share what they have written down with the class. Tell
students to add to their lists as they read the section to come. Explain that they will
have a chance to share additions to their lists after they have completed the section.
Explore and Explain
• Have students work in pairs to summarize the importance of sunlight to
life on Earth, which is discussed on page 463 of the Student Book. (Sample
answer: provides the energy necessary to heat Earth, provides the energy for
photosynthesis in plants, which are the basis of the food chain).
• Go on to introduce the subsection “Light Is an Electromagnetic Wave” on
page 464 of the Student Book to lead students in to the modern theory of
light and electromagnetic radiation. Have students work in pairs to preview
the vocabulary terms and their definitions in the section. Then discuss the
section with students. Ask, What are the characteristics of electromagnetic waves?
(they do not need a medium to move through; they travel at the speed of light)
Ask, What are some examples of types of electromagnetic waves? (radio waves,
microwaves, infrared light, visible light, ultraviolet light, X-rays, gamma rays)
• Students will benefit from going over Figure 5 on page 465 of the Student
Book. Explain the following points:
– The spectrum shows all forms of electromagnetic radiation, including
visible light. Non-visible waves include radio waves, microwaves, infrared
light, X-rays, and gamma rays. Have a volunteer point to the non-visible
regions of the spectrum. Explain that these forms are just like visible light
in many ways—our eyes are simply not capable of detecting them.
– Have a volunteer locate the narrow band that shows visible light. Indicate
that the “rainbow spectrum” below is an expansion of this small part of the
spectrum.
– Point out that wavelengths change size throughout the spectrum. Tell
students that wavelength is measured from one peak to the next. Ask, What
is an example of a wave with a long wavelength? (e.g., radio wave) What is
a wave with a short wavelength? (e.g., gamma wave) Where does visible light
fall on the spectrum—toward the short or long wavelength part of the spectrum?
(in the middle) Explain that shorter wavelengths have higher energy, and
longer wavelengths have lower energy.
• Have students complete Research This: Protecting Yourself from the Sun
to familiarize themselves with some very well known forms of electromagnetic
radiation, their effects on the human body, and ways to control them (next page).
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Writing Tip
Writing a Persuasive Text
Encourage students to
learn to be better writers
by paying close attention
to what they read. In
particular, have them read
through this section of the
Student Book to identify
the main idea or opinion
in various paragraphs. Ask
students to suggest ways
to rephrase the statement
or to provide a new one of
their own. This practice will
help students when they
need to write on their own.
Writing Tip
Writing a Persuasive Text
Explain that facts,
statistics, examples, and
reasons are needed to
support the opinion that
one expresses in a topic
sentence. Using facts,
statistics, examples, and
reasons makes one’s
writing more credible, and
thus, more persuasive.
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RESEARCH THIS PROTECTING YOURSELF FROM THE SUN
Skills
• Researching, Analyzing the Issue, Communicating,
Evaluating
Purpose
• To learn more about the health concerns related to
Sun exposure
Notes
• You may wish to assign this activity for homework.
• Encourage students to use reliable sources,
such as government, magazine, and educational
sites, to conduct their research. Have students
look for bias in the sources they use. In particular,
information about the health concerns associated
with tanning lamps may be heavily biased
depending upon the source of funding for the
research.
• Refer students to Skills Handbook 4. Research
Skills for help with conducting research and using
the Internet.
Suggested Answers
A. Exposure to the Sun’s rays is necessary for us to
produce vitamin D in our bodies; the vitamin D helps
us to absorb calcium for stronger, healthier bones.
B. Sunlight contains UVA and UVB rays, which can
cause skin aging, sunburn, cataracts, immune
system damage, and skin cancer.
C. The UV index is a scale ranging from 1 to 111. A
low number indicates a small UV risk and a very
high number indicates an extreme UV risk. The
UV index is predicted for each day and takes into
account clouds and other local conditions.
D. UVA rays are lower in frequency and energy than
UVB rays. UVA rays readily pass through the ozone
layer and reach Earth’s surface, whereas a great deal
of the UVB rays are absorbed by the ozone layer.
Enough UVB reaches Earth’s surface, however, to be
dangerous.
E. SPF stands for “sun protection factor.” It is a
number that describes how effective a sunscreen
product is at blocking UV radiation from the Sun.
A higher number means greater protection.
F.
Sunblock contains materials that physically
block sunlight from reaching skin, effectively
shading the skin. Sunscreen, on the other hand,
contains chemicals that absorb or reflect specific
frequencies of UV rays and only allow some of the
UV radiation to reach the skin.
G. Answers will vary. In general, light-skinned
individuals need a higher SPF sunscreen than
darker-skinned individuals.
H. You can limit your time outdoors to the early
morning and late afternoon when the Sun’s rays
have to pass through more of the atmosphere.
You can also wear sunglasses and clothing that
covers more of your skin, along with a brimmed
hat to shade your head and neck.
I.
Tanning beds mainly use UVA radiation. Sunlight
also contains UVA radiation, but has significantly
more UVB radiation than tanning beds.
J.
Answers will vary but should include information
about the types of UV radiation that reach Earth’s
surface, the dangers they pose, and what can be
done to avoid harm from them.
• Have students examine Table 1 on page 466 of the Student Book. Discuss the
positive and negative effects of electromagnetic waves. Students may notice
that the waves of lower energy do not seem to have any negative effects listed
(next page), but that the waves of higher energy have both positive and
negative effects. While the table does not explicitly state the dangers
associated with X-rays, ask students if they have ever had an X-ray performed.
Ask what precautions were taken by the technician (lead apron, for example).
• Move on to visible light, illustrated by Figure 7 on page 467. Explain that
what we see as white light is actually composed of a continuous sequence of
colours. While the sequence is continuous, meaning that there are various
shades of each of the colours, the colours red, orange, yellow, green, blue,
indigo, and violet and the ones usually identified with the visible spectrum.
• Have students complete Try This: Viewing the Visible Spectrum (next
page). By doing this activity, students will witness first-hand how light can be
broken up into the visible spectrum and then rebuilt into white light.
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T RY THIS
VIEWING THE VISIBLE SPECTRUM
Skills
• Predicting, Observing, Analyzing, Communicating
Purpose
• Students will use prisms to view the visible spectrum.
Equipment and Materials (per group): a ray box;
two triangular prisms; a sheet of white paper
Student Safety
• Remind students to be careful to avoid cutting their
fingers if the prism is chipped.
• Remind students to pull on the plug itself, not the
electric cord, when they unplug the ray box.
Notes
• Have students work in pairs for this activity.
• Move throughout the class to make sure that the
groups are properly positioning their ray boxes and
their prisms. Provide suggestions and assistance in
the event that students are having trouble getting
their equipment properly aligned.
• Encourage students to think about their predictions
in Part B before attempting the steps. Some
students may be inclined to perform the steps
without making a prediction. Explain that predicting
is an important skill and step in science and that it is
okay if the prediction is incorrect.
• It is unlikely that students will get a perfect
recombination back to pure white light. It is more
likely that students will get a grey light, perhaps
with some slight colour banding visible on the
fringes (depending on the quality of the prisms
used). The main idea is that a recombination of sorts
does occur, and the explicit banding visible with just
one prism disappears with the application of the
second prism.
• If time permits, distribute BLM 11.1-1 Try This: Can
Colours Be Split? to extend what students have done
and learned in the Try This activity from the Student
Book. The activity in the BLM makes use of the same
equipment and setup as the activity in the Student
Book, with the addition of cardboard and scissors. This
activity will allow students to explore the possibility of
further splitting the colours of the visible spectrum into
which white light was split in the first activity.
Suggested Answers
A. Answers will vary, but the seven colour bands are
red, orange, yellow, green, blue, indigo, and violet.
Students may have difficulty seeing the difference
between blue and indigo and also seeing the deep
violet colours.
B. Sample answers: Dew drops in sunlight produce
tiny spectra, and rainbows after storms are large
visible spectra. Halos around the Moon and Sun
can also show a spectrum much like a rainbow.
C. I predicted that the prisms would recombine
a spectrum back into white light and that two
prisms were required to do this. My prediction
was correct because two prisms did combine the
spectrum back into white light, although not
perfectly. The light was not completely white,
more light grey, but the distinct bands of the seven
colours definitely disappeared with the application
of the second prism. If properly placed, the second
prism should cause the spectrum of colours from
the first prism to recombine into white light.
D. Sample answer: White light is composed of light
of seven colours: red, orange, yellow, green, blue,
indigo, and violet.
• To further students’ understanding of the visible spectrum, you may wish to
have students complete BLM 11.1-1 Try This: Can Colours Be Split?
• Students should also understand that visible light is not the only form
of light that can be used to study outer space. Discuss how parts of the
electromagnetic spectrum other than visible light can be used to learn about
the universe. Refer students to Figure 11 on page 468 of the Student Book.
Explain that this image shows four images of the same galaxy, each taken with
a telescope that detects a different form of radiation. Each type of telescope
provides different information about the galaxy, which increases scientists’
understanding of it.
Extend and Assess
• Have students look again at the facts they wrote down about visible light in
the Engage activity, and ask volunteers to share what they have written down
with the class. Challenge students to add to their lists. Ask volunteers to
describe any additions or corrections they made to their lists after reading the
section.
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At Home
Have students look in their
homes for devices that
use the electromagnetic
spectrum. Have them
select one individual
device and share with
their families how the
electromagnetic spectrum
is related to their chosen
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• As an extension, invite students to further examine the use of electromagnetic
waves to explore deep space as shown in Figure 11. Have each student select
a specific topic of research, and prepare a presentation to share their findings
with the class. Students should select the method of presentation most
comfortable for them (e.g., oral, poster, multimedia).
• Have students complete the Check Your Learning questions on page 469 of
the Student Book.
CHECK
YOUR LEARNING
Suggested Answers
1. Conduction and convection transfer energy through a medium, whereas radiation transfers energy through
empty space.
2. Maxwell predicted that electromagnetic waves should be able to travel through empty space and would move at
the speed of light.
3. Hertz discovered radio waves in 1887 and Roentgen discovered X-rays in 1895.
4. microwaves, infrared light, red light, X-rays, gamma rays
5. Sunscreen protects the skin from ultraviolet light.
6. red, orange, yellow, green, blue, indigo, and violet
7. Objects in the universe emit many forms of electromagnetic radiation besides visible light. When we detect these
other forms of radiation we can view celestial objects and events in greater detail.
8. Sample answers: radio, television, microwave oven, cellular telephone, DVD remote control.
9. (a) X-rays, baggage screening; (b) ultraviolet light, vitamin D; (c) radio waves, radar; (d) infrared light, DVD remote
control; (e) microwaves, telecommunications; (f) gamma rays, cancer treatment; (g) visible light, theatre/concert effects
10. Students’ mind maps should list the following typical physical properties of light: transfers energy; can travel
through empty space; travels extremely fast; travels in straight lines, causing objects to cast sharp shadows; shows
wave-like properties; occurs in visible and invisible forms.
11. You could shine white light through a prism to produce a rainbow of colours and then shine the colours through a
second prism to re-form white light.
DIFFERENTIATED INSTRUCTION
Biology Connections
Discuss the light-absorbing
properties of chlorophyll.
Photosynthetic plants
contain pigments, most
notably chlorophyll, which
absorb and reflect specific
wavelengths of visible
light. The light energy
absorbed by the pigments
is used in the chemical
reaction photosynthesis.
Most green plants will die
if given only green light—
green light is reflected by
chlorophyll, not absorbed
for use.
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• Students may be confused because Figure 5 shows the components of the
electromagnetic spectrum in a horizontal format, whereas Table 1 describes
the components of the electromagnetic spectrum in a vertical format. Have
students work in pairs to create a diagram that combines the information in
Figure 5 with the information in Table 1. Have each pair of students share
their completed diagram with the class. This activity will be particularly
beneficial to visual/spatial learners, but is effective for all students.
ENGLISH LANGUAGE LEARNERS
• Write “ultraviolet” on the board. Then draw a line between “ultra” and
“violet”. Explain that “ultra” means “higher” or “beyond” and that the reason
for the name “ultraviolet” is that this particular type of light is at a “higher”
frequency than the violet light of the visible spectrum. Encourage students to
analyze other words, identifying suffixes and prefixes that will provide clues to
the meaning of the word.
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