DSCYF EDUCATION UNIT
Total marks: _________/ 30
Learning Goals for this Lesson
12/17/14 M.Dadisman
Investigating selective absorption of waves.
Students Will Know
Incident waves can be reflected by the surface of
an object or they may enter the object by
refraction.
Standards
Standard 3.1 & 3.3
Students Will Be Able To
Describe the characteristics of the key sections of
the electromagnetic spectrum and their practical
uses.
Lesson Essential Question
How do waves transfer energy?
Activating Strategy:
Energy Across Systems
Pre-Learning Concept Check
Key vocabulary to preview
Oscillation, cycle, crest, trough, equilibrium line, amplitude, period, frequency
Vocabulary strategy
Create foldable with tabs
Lesson Instruction
Learning Activity 1
Power point on types of electromagnetic waves.
Assessment Prompt for Learning Activity 1
Have the students list 2 examples of each type of EM wave with a
partner.
Learning Activity 2
Let’s investigate How waves transfer energy activity with gelatin and
lasers.
1. Shine the red (Helium-Neon) laser into both dishes of gelatin.
Make a drawing in your journal of this mini-investigation and
Graphic Organizer
Foldable
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record your observations.
2. In your journal explain the results. Why did they produce two
distinctively different outcomes?
3. If you are having difficulty explaining why the light behaves
differently in the two dishes of different colored gelatin, think
energy! It may be easier to explain what you observe by
thinking about the laser beam as a ‘stream’ of EM energy. What
happens to the energy coming from the laser? Where does it
go? Does it change forms? What evidence supports this
conclusion?
Assessment Prompt for Learning Activity 2
Discussion on the results of the lab.
Learning Activity 3
“How light divides” lab
Fill the container about 80% with water and then add in a few
drops of milk (coffee creamer works well also) to make the water
slightly cloudy.
Have a student hold the laser on a slight downward angle so that
the beam shines directly on the box. You may choose to mount
the laser to something to ensure the laser beam stays fixed at a
suitable angle, and will not accidently move.
As the laser beam is shining on the box, sprinkle chalk dust
between the laser and the container (or use a fogging agent) to
show the incident beam, the reflected beam and the transmitted
beam. Students will also be able to see (because of the milk fat
particles in the water) that some of the laser light is absorbed
inside of the container.
Assessment Prompt for Learning Activity 3
Question #1: Why couldn’t you see the laser beam traveling through
the air? Why could you see this beam if it passed through fog or chalk
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dust?
Question #2: What happened to the energy carried by the laser beam
that was absorbed by the water?
Learning Activity 4
Students make a poster that has the names of each of the 7
electromagnetic wave types & 2 examples (14 total examples-either
written or drawn)
Assessment Prompt for Learning Activity 4
Share/present posters with class
Learning Activity 5
Go for a physical or mental walk (go outdoors if able to; if not, stay
indoors and brainstorm and/or show video clips) and have students
identify as many examples of EM waves as they can.
Assessment Prompt for Learning Activity 5
Share the lists and student with highest # of accurate examples
receives a prize
Learning Activity 6
Selective absorption of waves investigation
1. Take two paper towels and fold them together. Then fold
them in half twice.
2. Place the folded towels into a microwave oven and turn the
oven on for 15 seconds. After the 15 seconds of exposure
to the microwaves, carefully remove the paper towels from
the oven. If you have a digital thermometer, record the
average temperature of the dry paper towels before and
after placing them in the microwave oven.
3. Next dampen the paper towels with room temperature
water and repeat the experiment. Be very careful when
removing the wet paper towels from the microwave oven;
they will probably be hot. If you have a digital thermometer,
record the temperature of the wet paper towels before and
after placing them in a microwave oven.
Assessment Prompt for Learning Activity 6
Question #1: Do the wet paper towels respond differently to the
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15 second exposure to the microwaves? Why / why not?
Question #2: Do the microwaves in a microwave oven carry
energy in the form of heat to the food?
Question #3: Why do you think a popcorn kernel ‘pops’ when
placed in a microwave oven? What might be ‘wrong’ with those
kernels that do not pop?
Learning Activity 7
Selection absorption of infrared light waves
1. Place the TV remote on the lab table and place the IR
probe roughly 10 cm from the remote. Be sure to face the
probe sensor towards the remote.
2. Open the program Investigating IR Waves. Start
collecting data (click on the green collect button on the
Logger Pro screen) while one of the TV remote keys is
depressed. A wave pattern should be visible on your
screen.
3. Now it is time to test materials to see if they absorb or
transmit the IR waves leaving the remote. Make sure to
position the sample material between the remote and the
sensor so that the IR waves must pass through the
material to reach the sensor. Then start collecting data
while one of the TV remote keys is depressed. A wave
pattern should be visible on your screen if the material
does not absorb IR waves. If the material absorbs or
completely reflects IR waves, the wave pattern may be
altered or non-existent.
4. Make a list of materials that you test and the outcome of
your investigation in your journal. Include numeric data if
possible. Later, your teacher may ask you to discuss your
findings.
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Assessment Prompt for Learning Activity 7
Question #1: Does the remote source emit a narrow focused
beam of IR waves, or does it emit a broad spreading beam?
Question #2: What materials allowed both visible light and IR
waves to pass?
Question #3: What materials allowed visible light waves to pass,
but blocked IR waves?
Question #4: What materials blocked visible light waves but
allowed IR waves to pass?
Question #5: Can IR waves be reflected by a standard mirror?
Question #6: You have just moved into a new house and the
dish/satellite Serviceman installs the receiver unit inside your TV
cabinet behind a glass door. Will the remote control signal be
affected by the glass door? Will the thickness of the glass
matter? Will it work if the door is wooden and not glass?
Learning Activity 8
Selective absorption of UV rays
1. You can create a testing “card” by cutting four holes in an
index card.
Three holes
will be for
testing
materials and
the fourth will
be the control.
For example,
you could
cover all four
holes with
light plastic and then place sunscreen lotion of 5 SPF, 15
SPF, and 45 SPF over three of the holes to test the
effectiveness of each sunscreen.
2. Open the file Investigating UV Waves. This
program will only record the intensity of the UV light
wave.
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3. Whatever approach you use to test how well materials
absorb or reflect UV waves, be sure to construct a data
table and record the results of your investigation. Repeat
your measurements if necessary or expand your
investigation by making a second card to test more
materials.
Write a summary of your results in your journal
Assessment Prompt for Learning Activity 8
Question #1: Why go to the trouble and expense of wearing sunblock? What would happen to the energy carried by the UV
waves if the waves struck bare skin?
Summarizing Strategy
In your journal, write a concise summary of this investigations. Be sure to
address the following questions and use your data to support your responses.
 What can happen to a wave when it strikes the surface of an object?
 What happens to the energy carried by a wave when the wave is absorbed by a material?
 What is selective absorption?
 What is selective reflection?
 Do all materials absorb and/or reflect EM waves the same way?
Energy Across Systems
Pre-Learning Concept Check
Below are several statements. Decide which of them you agree with them or disagree
with the statement. Write a sentence or two describing the reasoning behind your choice.
A. When a wave strikes a substance, its energy will be absorbed.
AGREE
DISAGREE
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B. When a wave is absorbed by a substance, its energy is used up.
AGREE
DISAGREE
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_______________________________________________________________________________
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C. All frequencies of EM waves are absorbed by the same substances.
AGREE
DISAGREE
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D. Energy that has been absorbed by a wave can be re-emitted by the substance.
AGREE
DISAGREE
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