Download Light Reflects (Part 1) Lesson 7

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Light Reflects (Part 1) Lesson 7 Grade 10, Science, Applied SNC2P
Critical Learning
Guiding Questions
•• The behavior of light depends on the materials with which it interacts.
•• How does light behave when it interacts with •
a converging mirror? a diverging mirror?
•• Characteristics of images found in mirrors can be represented.
•• The fundamental concept of structure and function focuses on the relationship
between the function of a human-made object and the form that the object
takes.
•• How can a ray diagram be used to describe
the characteristics of an image formed when
light reflects from the surface of a converging
mirror? a diverging mirror?
•• What are some applications of converging •
and diverging mirrors?
Curriculum Expectations
Scientific Investigation Skills and Career Exploration
A1. Demonstrate scientific investigation skills (related to both inquiry and
research) in the four areas of skills (initiating and planning, performing and
recording, analyzing and interpreting, and communicating)
A1.5 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
A1.6 gather data from laboratory and other sources, and organize and
record the data using appropriate formats, including tables, flow
charts, graphs, and/or diagrams
A1.8 analyze and interpret qualitative and/or quantitative data to
determine whether the evidence supports or refutes the initial
prediction or hypothesis, identifying possible sources of error, bias, or
uncertainty
A1.10 draw conclusions based on inquiry results and research findings, and
justify their conclusions A1.11 communicate ideas, plans, procedures, results, and conclusions orally,
in writing, and/or in electronic presentations, using appropriate
language in a variety of formats
A1.12 use appropriate numeric, symbolic, and graphic modes of
representation, and appropriate units of measurement
Learning Goals
Students will be able to:
•• use ray diagrams to illustrate observations using
converging and diverging mirrors
•• use the laws of reflection to predict and
explain the characteristics of images formed in
converging and in diverging mirrors
•• use investigation skills of performing and
recording, analyzing and interpreting, and
communicating
•• construct an optical device that uses a variety
of mirrors
Physics: Light and Applications of Optics
E2. Investigate, through inquiry, properties of light, and predict its behaviour in
mirrors and as it passes through different media
E2.1 use appropriate terminology related to light and optics including but
not limited to: angle of incidence, angle of reflection, angle of refraction,
centre of curvature, focal length, luminescence, magnification, principal
axis, radius of curvature, and vertex [C]
E2.2 use an inquiry process to investigate the laws of reflection; use these
laws to explain the characteristics of images formed by converging
and diverging mirrors; and draw ray diagrams to illustrate their
observations [PR, AI, C]
E2.7 construct an optical device that uses a variety of mirrors [PR]
E3. demonstrate an understanding of characteristics and properties of light,
particularly with respect to reflection and refraction and the addition and
subtraction of colour
E3.4 describe qualitatively how visible light is refracted at the interface
between two different media
L I T E R AC Y G A I N S T R A N S F O R M I N G I N S T R U C T I O N A L P R A C T I C E S U P P O R T S G R A D E 10 SCIENCE
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Light Reflects (Part 1) Lesson 7 Grade 10, Science, Applied SNC2P
Instructional Components and Context
Readiness
•• Ray diagrams (from Lesson 6)
•• Terminology (from Lesson 6)
•• Collaborative norms and skills, e.g., taking
roles, taking turns, disagreeing agreeably
Terminology
•• Converging (or concave) mirror
•• Diverging (or convex) mirror
•• Focal point
•• Principal axis
•• Vertex
Resources
Websites
•• Hands On Optics
•• Gizmos
•• Optics Videos
•• Radio telescope
Materials
•• Optical devices (actual or images) with converging and/or diverging mirror(s), e.g., spoon, satellite dish, make-up mirror, surveillance
(wide-angle) mirror, reflecting telescope, microscope, car headlight, flashlight, funhouse mirror
•• Converging mirror (large), diverging mirror (large)
•• Optical bench with a candle (or other luminous object) and a converging and a diverging mirror
•• Spotlight on Investigation worksheet
L I T E R AC Y G A I N S T R A N S F O R M I N G I N S T R U C T I O N A L P R A C T I C E S U P P O R T S G R A D E 10 SCIENCE
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Light Reflects (Part 1) Lesson 7 Grade 10, Science, Applied SNC2P
Minds On (Elicit, Engage)
Whole Class ➔ Demonstrating Converging and Diverging Mirrors
Place an object in front of a large converging mirror. While students are observing, elicit
responses to the following questions: Where should the mirror be held so that the image is upright?
upside down? larger than real life? smaller than real life? the same size as it is in real life? How is the
image produced from this mirror different from that produced by a plane mirror?
Place an object in front of a large diverging mirror. Elicit student responses to the same questions
as above.
Pause and Ponder
•
QuickTip
If only small converging and
diverging mirrors are available,
this demonstration should be
done as a small group activity.
Whole Class ➔ Previewing Learning Goals
Share the learning goals and guiding questions. Review any safety procedures pertinent to this
lesson.
Small Groups ➔ Investigating Mirrors in Optical Devices
Set up stations with a variety of optical devices (e.g., telescope, microscope) that use converging
and diverging mirrors and chart paper for graffiti.
Form groups and assign each group to a station. At each station, students examine the optical
devices. Based on their investigations, students select one or more questions on optical devices
using mirrors and record answers to their selected questions on the graffiti chart paper.
Each group visits each station and reviews the information on the graffiti. Groups add any
additional information and address one or more of the remaining questions. At the last stop,
groups use the graffiti and prepare an oral summary of key ideas. Debrief by inviting each •
group to report.
Use the learning
goals and guiding questions
as prompts to introduce the
Action! and to provide students
opportunities to reflect on
learning throughout the lesson. See Metacognition Guide.
Action! (Explore, Explain)
•
•
•
•
•
Small Groups ➔ Investigating Using Converging and Diverging Mirrors
Using interactive software, such as Gizmo, “Light rays with mirrors” and Light rays task (based
on the Exploration Guide in the Gizmo activity), students demonstrate how to construct a ray
diagram to locate the image produced by a converging and a diverging mirror.
Use information from light
rays task to inform instruction and
plan guided practice.
Students use an optical bench to project a real image of the candle, using a converging mirror.
They compare what happens when using a diverging mirror. Students prepare a ray diagram for
each case which includes labels for the principal axis and the vertex.
Whole Class ➔ Drawing Conclusions
Debrief by inviting one student from each group to report the group’s observations and guide
them to make conclusions about what they observed. Extend the discussion by asking students
to compare the experiences of using the interactive software and the optical bench, (e.g., which
helped you understand the phenomenon more clearly?).
Prompt students to
compare their observations •
with what they are hearing •
from other groups.
Facilitate a discussion about some of the applications of converging and diverging mirrors and list
some examples.
Small Groups/Pairs/Individual ➔ Applying Knowledge to Build an Optical Device
Using at least two mirrors (plane, converging or diverging), students construct an optical device
for a practical application, (e.g., a periscope to see over a tall fence.) (Note: specify the height of
the fence), kaleidoscope, a busybody (http://www.kilianhardware.com/franbus.html).
QuickTip
Students identify the purpose of the device, thereby indicating the problem or challenge the
device will solve.
As an extension, students can use
mirrors to create optical illusions.
See http://www.moillusions.
com/2006/05/cylinder-mirroroptical-illusion.html and
http://www.visualillusion.net/
Chap14/ for examples.
Consolidation (Elaborate, Evaluate, Extend)
•
Whole Class/Individual ➔ Gathering Information for Culminating Task
Review the anchor chart listing the various technologies (from Lesson 1). Add any additional
technologies. Pose the questions: Which of these technologies use mirrors? How do they use them?
Students jot notes and any questions for their assigned technology in their project log.
L I T E R AC Y G A I N S T R A N S F O R M I N G I N S T R U C T I O N A L P R A C T I C E S U P P O R T S G R A D E 10 S C I E N C E Use the project logs to
inform instruction and assess
progress toward the culminating
activity. Also use the information
to see if some students may need
to select a different technology.
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Light Reflects (Part 1) Lesson 7 Grade 10, Science, Applied SNC2P
Minds On (Elicit, Engage)
Safety Procedures
Teachers must model safe practices at all times and communicate safety expectations to students in accordance with school board and
Ministry of Education policies and Ministry of Labour regulations. Teachers are responsible for ensuring the safety of students during
classroom activities and also for encouraging and motivating students to assume responsibility for their own safety and the safety of
others. Teachers must also ensure that students have the knowledge and skills needed for safe participation in science activities.
To carry out their responsibilities with regard to safety, it is important for teachers to have:
•• concern for their own safety and that of their students
•• the knowledge necessary to use the materials, equipment, and procedures involved in science safely
•• knowledge concerning the care of living things – plants and animals – that are brought into the classroom
•• the skills needed to perform tasks efficiently and safely
Students demonstrate that they have the knowledge, skills, and habits of mind required for safe participation in science activities
when they:
•• maintain a well-organized and uncluttered work space
•• follow established safety procedures
•• identify possible safety concerns
•• suggest and implement appropriate safety procedures
•• carefully follow the instructions and example of the teacher
•• consistently show care and concern for their own safety and that of others
Various kinds of health and safety issues can arise when learning involves field trips. Out of- school field trips can provide an
exciting and authentic dimension to students’ learning experiences. They also take the teacher and students out of the predictable
classroom environment and into unfamiliar settings. Teachers must preview and plan these activities carefully to protect students’
health and safety. The Ontario Curriculum, Grades 9 and 10: Science, 2009
Graffiti
Graffiti is a collaborative learning strategy that structures generating ideas, critical reflection on those ideas, and summarizing skills.
Method:
1. Distribute a sheet of chart paper to each group. On each sheet is written a different question or prompt.
2. Each team collaboratively responds to the question or prompt, using a different coloured marker. 3. At a signal, teams rotate to another sheet/prompt, taking their coloured marker with them. They record a collaborative response.
4. Repeat until teams return to their original sheet.
5. Teams critically consider all responses and then summarize key ideas.
6. Teams report out to the whole group.
See Think Literacy Subject-Specific Examples: English, Grades 10-12, p. 28. Questions on Optical Devices Using Mirrors
•• What is the device’s most common use?
•• Does it use a converging or a diverging mirror?
•• Where is the mirror?
•• What function does the mirror serve?
•• How would modern life be different without the device? Consolidation (Elaborate, Evaluate, Extend)
Anchor Chart
An anchor chart is a strategy for capturing students’ voices and thinking. Anchor charts are co-constructed. By making students’ thinking
visible and public, they “anchor,” or stabilize and scaffold classroom learning. Anchor charts should be developmentally appropriate and
clearly focused, accessible, and organized.
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Light Rays Task
page 1 of 2
The Gizmo shows: • actual light bulb in front of the mirror (to the left of the mirror in this view)
• the mirror in the middle
• the image of the light bulb formed by the mirror
Activity A: Concave Mirrors
Get the Gizmo Ready:
• Under ‘Show Lines,’ uncheck all three (3) lines: Parallel Line, Central Line, and Line through Focal Point
• Under ‘Show specific line segments’ uncheck all checkboxes.
• Select a ‘Concave Mirror’ from the drop down list.
1. Drag the light bulb to just above -4 on the principal axis and place the focal point (blue dot) on -25.
a) Where does the image appear?
b) In this situation is the image larger of small than the actual bulb?
2. Slowly drag the focal point closer to the mirror.
a) How does this affect the curvature of the mirror?
b) How does this affect the image?
3.Place the focal point at -10. Drag the light bulb slowly to the left, away from the mirror.
(Keep the bulb near the principal axis to prevent the image from getting too blurry.) •
Watch the image as you drag the bulb.
a) When is the image behind the mirror?
b) When is the image in front of the mirror, where the actual bulb is?
c) When is the image upside-down?
d) When is the image the largest?
To understand the behavior of the image you just saw, it helps to explore how individual rays of light are reflected. •
Place the bulb just above -25 and the focal point at -10. Select Colorize lines, and turn on the Parallel line and the
Original light lines only.
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Light Rays Task
page 2 of 2
Drawing Ray Diagrams: Understand the Behavior of the Image
1. Predict: How do you think this ray of light, parallel to the principal axis, will be reflected off the concave mirror?
Explain.
2. Turn on Reflected Light Lines.
a) How is the parallel ray reflected?
b) What two (2) things do all parallel rays of light pass through? (Hint: Move the bulb around a bit to verify your answer.)
3. T urn OFF the Parallel Line and turn ON the Line Through Focal Point only, with BOTH Original and Reflected light rays
visible. Move the light bulb around a bit.
a) How does this ray of light reflect off a concave mirror?
4.Turn OFF the Line through Focal Point and turn ON the Central Line only, still with both Original and Reflected Rays
visible. Move the bulb around. Notice that the central line strikes the mirror directly at the principal axis.
a) How does it reflect? Compare this light reflecting off a PLANE mirror.
5. Turn on all three (3) lines, both original and reflected, and drag the bulb around.
a) Where does ALL reflected light meet?
6. W
hen an object is beyond the focal point of a concave mirror, a real image is formed that is upside down and in front
of the mirror. The image is called “real” because it is formed by actual reflected light and would be visible on a screen or
piece of paper. Drag the bulb around between roughly -15 and -30.
a) When is the image larger than the actual bulb? When is the image smaller?
b) When do the image and the bulb seem to be the same size? How does this relate to the location of the focal point?
7. A
concave mirror can produce an image behind the mirror. To see how this occurs, place the light bulb near the mirror,
just above -4 (near the axis). Be sure the focal point is still at -10. Set the Gizmo so that only the Original and Reflected
Light Lines of the Parallel Line are shown. Turn on Apparent Light Line. This dotted line shows the path of light your
brain perceives. NOTE: It is NOT an actual light ray.
a) What lies on the apparent light line?
8. Turn on the other two (2) rays of original emitted light. Move the light bulb around.
a) Where do the three (3) apparent light lines meet? This type of image is called a Virtual Image.
Activity B: Convex Mirrors
1.
Turn off All Light Ray and select a ‘Convex Mirror’
a) How is the shape of a convex mirror different from that of a concave mirror?
b) Where is the focal point of a convex mirror located?
c) Drag the bulb around. Where is the image always located?
d) How does the size of the image compare to the size of the bulb? Is this always true?
2. Turn on the Parallel Line, and the Original and Reflected rays. Drag the bulb around.
a) Do parallel rays of light converge or diverge when reflected off a convex mirror?
b) Is there a point at which all the reflected light meets?
3. Turn ON all three (3) rays of light. Then turn on Apparent Light Lines and drag the bulb around.
a) Where do the apparent light lines meet?
b) Is this image real or virtual? Explain why?
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