LIGHT REFLECTION
Science Concept:
When light waves reflect off a surface, the angle of incidence is equivalent to the angle of reflection.
Objectives:
The student will:
t diagram the Law of Reflection;
t make generalizations describing the relationship of the angle of incidence and the angle of reflection;
and
t display data in a table.
GLEs Addressed:
Science
[9] SB4.3
The student demonstrates an understanding of motions, forces, their characteristics, relationships,
and effects by describing the interactions of waves (i.e., reflection, refraction, wave addition).
[9] SA1.1 The student demonstrates an understanding of the processes of science by asking questions,
predicting, observing, describing, measuring, classifying, making generalizations, inferring, and
communicating.
Math
[9] S&P-1 The student demonstrates an ability to classify and organize data by designing, collecting,
organizing, displaying, or explaining the classification of data in real-world problems (e.g., science or
humanities, peers, community, or careers) using information from tables or graphs that display two
sets of data or with technology.
Vocabulary:
angle of incidence - the angle between a line or ray of light or heat, called the “incident line,” and a line
perpendicular to the surface, at the point when the line meets the surface
angle of reflection - the angle that a reflected ray of light, heat, beam, etc., makes with a perpendicular to the
surface, at the point of reflection
normal - a vector (or line) that is perpendicular to a surface
Law of Reflection - the principle that when a ray of light, radar pulse, or the like, is reflected from a smooth
surface, the angle of reflection is equal to the angle of incidence, and the incident ray, the reflected
ray, and the normal to the surface at the point of incidence all lie in the same plane
reflection - the return of light, heat, or sound after striking a surface without it being absorbed
Materials:
t
t
t
t
t
t
t
t
t
Plane mirrors (one per group)
Laser light (one per group)
Laser safety goggles (one per student)
Powdered milk (1/2 cup per group)
Cups (one per group)
Plain white paper
Protractor (one per group)
Science journal
STUDENT WORKSHEET: “Golf”
Science Teacher Education Program ©2009 Geophysical Institute, UAF
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Light Reflection
LIGHT REFLECTION
Activity Procedure:
1.
Set up paper & mirror on table in the front of the class as depicted below.
Mirror Paper 2.
90! angle between mirror and paper (stack books behind to keep up) Pour powdered milk into a cup for each group.
Activity Procedure:
Please refer to the assessment task and scoring rubric located at the end of these instructions. Discuss the
assessment descriptors with the class before teaching this lesson.
Gear Up
Process Skills: observing, inferring and communicating
1. Have students stand around the table so they can see. Ask students to predict what will happen when
the laser is pointed at the mirror. Record predictions on the board with each student’s initials beside
their response.
2. Point the laser at the mirror and sprinkle some powdered milk over the light so that students can see the
light
3.
4.
Ask students what happens if the angle of the laser is changed. Record their predictions on the board
with each student’s initials beside their response.
Explain students will use this set-up to further explore light reflection.
Explore
Process Skills: observing, communicating, measuring, and collecting data
5. Introduce the vocabulary terms by listing them on the board and having students help to define them.
Leave the defined words on the board for further reference.
6. Divide students into groups of three and let students chose a specific job. The jobs include:
a. Recorder - writes for the group during the investigation
b. Laser light Operator – operates the laser light, maintains it at safe distances and angles away from
eyes of group members; also is responsible for asking the teacher any questions that the group
cannot figure out
c. Powder Milk Distributor- gently sprinkles powder milk to illuminate the beam of light from the
laser light
7. Distribute paper, mirror, laser, protractor, and powdered milk to each group. Challenge groups to find
Science Teacher Education Program ©2009 Geophysical Institute, UAF
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Light Reflection
LIGHT REFLECTION
the relationship between the incoming ray and the reflected ray. Students should collaborate and decide
on what method they will use to collect data. Students should rotate jobs throughout the investigation.
8. Instruct students to set up their paper and mirror. Review laser safety procedures. Dim the lights and
allow students to proceed.
Generalize
Process Skills: describing, inferring, comparing, and making generalizations
9. Bring students back together and ask students the following questions:
a. What type of pattern did you notice in your angle measurements?
b. What does this pattern tell you?
c. What might happen if the mirror was concave? Convex?
d. What would happen if the surface were made of a transparent material? (NOTE: This could lead
into a discussion of refraction.)
Apply
Process Skills: communicating and describing
10. Ask students to explain, in their science journal, how a periscope works.
Science Teacher Education Program ©2009 Geophysical Institute, UAF
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Light Reflection
Science Teacher Education Program ©2009 Geophysical Institute, UAF
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Light Reflection
[9] SA1.1
[9] S&P-1
The student displays data in a table.
[9] SB4.3
The student diagrams the Law of
Reflection.
The student makes generalizations
describing the relationship of the angle
of incidence and the angle of reflection.
GLE
Objective
Rubric:
The student does not
display data in a table.
The student does not make
a generalization of the
relationship of the angle of
incidence and the angle of
reflection.
The student diagrams the
Law of Reflection with less
than three labels/
descriptions.
Below Proficient
The student correctly
displays data in a table but
is missing either labels or
units.
The student makes a correct
generalization of the
relationship between the
angle of incidence and the
angle of reflection.
The student diagrams the
Law of Reflection with three
correct labels/descriptions.
Proficient
The student correctly displays
data in a table with both labels
and units.
The student makes a correct
generalization of the relationship
between the angle of incidence
and the angle of reflection. A
correct example or diagram is
included in the description.
The student diagrams the Law of
Reflection with more than three
correct labels/descriptions.
Above Proficient
1. Using your knowledge of the Law of Reflection, determine where he should he “hit” the sidewall and where the ball will bounce. On STUDENT
WORKSHEET: “Golf,” label the diagram to show the path the ball will take. The diagram should include at least three labels with descriptions.
2. Include a generalization that describes the relationship between the angle of incidence and the angle of reflection. The description may include a
diagram or example of the relationship.
3. Make a table that displays the angle of incidence and angle of reflection necessary to get a hole-in-one from positions A, B and C. The table should
include labels or units. It may include both.
Scenario: Danny is playing miniature golf and would like to get a hole-in-one when the ball is at position A. The course has an obstacle, so he must bounce
the ball off the sidewall.
Assessment Task:
LIGHT REFLECTION
NAME: __________________________
GOLF
Scenario:
Danny is playing miniature golf and would like to get a hole-in-one when the ball is at position A. The course has
an obstacle, so he must bounce the ball off the sidewall.
Directions:
Using your knowledge of the Law of Reflection, determine where Danny should “hit” the sidewall and where the
ball will bounce. Label the diagram below to show the path the ball will take. The diagram should include at
least three labels with descriptions.
1.
Label the diagram showing the path, from position A, to make a hole-in-one.
Sidewall Ball A B C Hole Obstacle 2.
Write a generalization that describes the relationship between the angle of incidence and the angle of
reflection. The description may include a diagram or example of the relationship.
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
3.
On the back on this sheet of paper, or on a piece of graph paper, make a table of the angle of incidence and
angle of reflection from the position A, B and C to the hole.
Science Teacher Education Program ©2009 Geophysical Institute, UAF
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Light Reflection