11.3
Time
45–60 min
Skills
Researching
Communicating
Other Program Resources
BLM 0.0-2 Venn Diagram
(comparing two items)
Skills Handbook 4. Research
Skills
Science Perspectives 10
website www.nelson.com
/scienceperspectives/10
The Laser—A Special Type of Light
OVERALL EXPECTATIONS
• demonstrate scientific investigation skills in the four areas of skills
• 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
SPECIFIC EXPECTATIONS
Scientific Investigation Skills
• identify and locate print, electronic, and human sources that are relevant to
research questions
Relating Science to Technology, Society, and the Environment
• analyze a technological device that uses properties of light and explain how it
has enhanced society
Related Resources
Gizmo: Laser Reflection
Developing Skills of Investigation and Communication
• use appropriate terminology related to light and optics
Hecht, Jeff. Beam: The
Race to Make the Laser.
Oxford University Press,
2005.
Science Perspectives 10
ExamView® Test Bank
Science Perspectives 10
Teacher eSource SUITE
Upgrade
Science Perspectives 10
website www.nelson.com
/scienceperspectives/10
KEY CONCEPTS
• Optical devices benefit our society in many ways.
• Light is produced by natural and artificial sources.
• Light is an electromagnetic wave that travels at high speed in a straight line.
EVIDENCE OF LEARNING
Look for evidence that students can
• describe the properties of laser light
• explain how lasers are used
▼
SCIENCE BACKGROUND
Lasers
• Lasers were first developed in the
late 1950s and early 1960s. There
have been continual changes and
improvements in laser technology
since that time. As indicated in
Section 11.1, laser is an acronym for
Light Amplification by Stimulated
Emission of Radiation.
• How exactly does a laser source
produce light? In an incandescent
light, the medium is the filament—
it gets heated and radiates light
at many different wavelengths in
many different directions. In a laser,
emission is much more controlled.
A medium (e.g., a ruby) is pumped
full of energy, causing a very high
percentage of the atoms to
reach highly excited states and
light is emitted by each atom.
▼
• There are three characteristics that
differentiate laser light from light
produced by other sources. The
electromagnetic waves produced
by a laser light are all at the same
wavelength and, therefore, produce
the same colour of light.
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Each light-emitting atom causes
a neighbouring atom to also emit
light at the exact same wavelength.
This is the critical step. The process
continues over and over and
throughout the medium, causing an
enormous number of atoms to emit
light at the exact same wavelength.
Special mirrors filter the laser so that
only the monochromatic light can
exit the medium. This monochromatic
light is the laser beam.
POSSIBLE MISCONCEPTIONS
Identify
• Students may think of lasers as weapons.
Clarify
• Explain that this perception comes from movies and television, not from
scientific fact. Lasers have many important applications.
Ask What They Think Now
• At the end of the section, ask, What are some uses of lasers? (Students should
recognize the many positive applications of lasers.)
TEACHING NOTES
Engage
• Engage students’ interest in the properties of lasers by discussing the Engage
in Science feature on page 460 of the Student Book. Use students’ discussion
of the feature to assess their prior knowledge of lasers. Tell students that the
following section will explain how light produced by a laser differs from light
produced by other sources.
• If possible, demonstrate a laser pointing device and a flashlight in the
room. Point out that the laser light is narrow and focused—not at all like a
flashlight. Ask, How is the bulb in a flashlight able to send out what appears
to be a focused beam? Have students try to answer the question. Guide
them to the idea that the flashlight bulb itself sends out light scattered in
all directions. It appears to be focused in a beam simply because a concave
mirror reflects the scattered light in a single direction. If possible, take the
flashlight apart to show the parts, in particular the location of the bulb and
the concave mirror responsible for making the focused beam of light.
Explore and Explain
• Point out Figure 1. Have students refer to the figure and describe how laser
light is different from light produced by an incandescent bulb. (The main
difference between light bulbs and lasers is that lasers emit only one type of
wave, whereas light bulbs emit a number of them.)
Distribute •BLM 0.0-2 Venn Diagram (comparing two items). Instruct students
to write the following headings on the Venn diagram: “Laser light” and
“Incandescent light.” Have students review the section and complete the
Venn diagram, showing how laser light and incandescent light are similar and
how they are different. Have students consider the following characteristics:
the colour of light produced, the intensity of light produced, and the
concentration of the beam of light produced.
• Have students complete the Research This: Lasers For Different Uses (next
page). This activity will help students to gain a better appreciation of the practical
applications of lasers and an understanding of the different types of lasers.
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RESEARCH THIS LASERS FOR DIFFERENT USES
Skills
• Researching, Communicating
Purpose
• Students will research characteristics and uses of
different types of lasers.
Notes
• Direct students to the Nelson Science Perspectives 10
Student eSource for weblinks related to this activity.
B. Sample answers: Carbon dioxide lasers emit
infrared light and are used in surgery and for
cutting materials. Krypton lasers emit various
colours of visible light and are used in light
shows. Nitrogen lasers emit ultraviolet light
and are used to measure air pollution and to
pump dye in dye lasers.
C. Excimer lasers, which produce ultraviolet light, are
used for LASIK, or laser eye surgery.
Suggested Answers
A. Helium-neon lasers produce visible light with a red
colour.
Extend and Assess
• Have students re-examine the information in this section. Then have students
write a short newspaper-style article with the title “How Lasers Are Used.”
Post students’ completed articles in the classroom. This assignment is an
opportunity to assess students’ understanding of the lesson.
• As an STSE extension, encourage students to research how laser light is
produced. They should produce a report or presentation in a format of their
choosing for communicating what they have learned to the rest of the class.
• Have students complete the Check Your Learning questions on page 478 of
the Student Book.
CHECK
YOUR LEARNING
Suggested Answers
1. Unlike light from incandescent sources, laser light is made up of waves that all have exactly the same energy and
that travel in unison in exactly the same direction. Light from a laser does not spread out as it travels.
2. The light leaving the prism will be green because laser light is made up of a pure colour.
3. (a) Laser light travels in exactly one direction, so a laser beam remains intense enough to travel to the Moon and
back and still be visible.
(b) The white light would spread out in all directions and would weaken too much before we could use it to
measure a great distance.
4. Owing to its natural intensity, laser light can harm your eyes.
5. The diagram should show that white light is made of many wavelengths travelling in all directions and not in
unison, but that laser light is a single wavelength with the waves travelling in unison in exactly one direction.
light bulb
laser source
6. Sample answers: laser lights in shows, laser eye surgery, laser scanners in grocery stores, lasers in optical drives,
cutting lasers in industry, laser pointers.
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DIFFERENTIATED INSTRUCTION
• All students, particularly mathematical/logical learners, may benefit from
summarizing chapter information in table form, as shown below. Copy the
table on the board and have students copy it and fill it in. (Sample answers
are provided.)
Does it
spread out?
Type of light
Wavelengths
Direction
Colours
Incandescent
Light
many different
scattered in all
directions
all colours of
the spectrum
yes
Laser Light
single
wavelength
single narrow
beam
single colour
stays focused
• Interpersonal and verbal/linguistic learners may benefit from explaining the
illustration in Figure 1 aloud to a partner. Within each student pair, have one
student first explain the illustration to their partner, and have the partner
pose one or more relevant questions. Then have students trade roles and
repeat the exercise.
ENGLISH LANGUAGE LEARNERS
• Focus on words that have multiple meanings, beginning with light. Ask
students to define light in as many ways as possible. Sample definitions might
include “not heavy,” “to ignite,” “a lamp,” “not strong,” “not serious,” “gentle.”
Have students create a sentence for each definition.
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At Home
Have students search their
homes for devices that
use a laser. They should
then choose one such
device and write a short
description of the device
and how it applies laser
technology. Ask students
to share their written
description with their
families and with the class.
Chapter 11 The Production and Reflection of Light
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