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The learning
activities in this Lesson will help students prepare to complete the GE
Lighting Audit for their school or home as they learn about the nature
of light.
This Lesson comprises five learning activities.
What
is Light? is a Read About that discusses the spectrum of electromagnetic
radiation including visible light. Students learn that light is made up
of photons, which can appear to be sometimes like waves and sometimes
like particles. For more information on related scientific concepts, see
More Background included in this Lesson Plan.
Separating
Light with a Prism is a Hands-on activity in which students use readily-available
materials to explore bending visible light and observe its component colors.
In Making
a Pinhole Camera, another Hands-on activity, students learn
that the eye works like a camera.
Reflecting
Light and Bending
Light are two Experiments your students can conduct with minimal materials,
independently, or in small groups.
- that EM
spectrum is a range of transmitted energy, of which visible light is
a part.
- that light
moves in waves, as well as in bundles of energy called photons.
- that white
light is a combination of all colors.
- that reflection
bends, or bounces, light backward.
- that refraction
bends and separates light.
- that the
eye sees images upside down.
The
chart below suggests options for incorporating the activities into your
schedule.
Activity
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Class
Periods Needed to Complete
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Teaching
Approaches to Consider
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Features
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1.
What Is Light?
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one
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Independent
reading
Guided
reading
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Before
Reading, During Reading, Vocabulary, and After Reading questions
Animation:
The Visible Spectrum
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Teaching
Ideas
- Review
student's KWL charts to identify misconceptions student's have
about light and its properties.
- Make
a T-chart on the board, labeling the sides "Light as Waves"
and "Light as Particles." Have students suggest details
about light, demonstrating each concept. You might organize small
groups to brainstorm ideas for each side. Compile the ideas into
one chart to complete the lesson.
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Activity
|
Class
Periods Needed to Complete
|
Teaching
Approaches to Consider
|
Features
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2.
Separating Light with a Prism
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one
or two
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Teacher
demonstration
Students
working in pairs or small groups
Independent
work at home
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Sidebar:
The Not-So-Blue Jay
Animation:
The Visible Spectrum
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Teaching
Ideas
-
See the student's page for this activity. You might organize small
groups to try the different versions suggested. Some can try different
light sources with one prism, some can attempt the two-prism set-up,
and some can try to create the prismatic effect with common objects.
- Give
small groups of students bubbles, bubble wands, and a large dish.
Have them make rainbows on the walls using them. Why aren't the
colors on the bubbles themselves in rainbow order?
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Activity
|
Class
Periods Needed to Complete
|
Teaching
Approaches to Consider
|
Features
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3.
Making a Pinhole Camera
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one
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Independent
work at school or at home
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Animation:
Inside a Pinhole Camera
Animation:
How We See
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Teaching
Ideas
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Activity
|
Class
Periods Needed to Complete
|
Teaching
Approaches to Consider
|
Features
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4.
Reflecting Light
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one
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Teacher
demonstration
Students
working in pairs or small groups
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Line
Graph: Temperature Changes Over Time
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Teaching
Ideas
- Some
demonstrations are difficult for a large group to see. Consider
having stations and parent demonstrators or organizing the experiments
in "circuits" around the room.
- Have
students complete a reflecting experiment. Cut a small hole in
a sheet of cardstock and tape a comb across the hole. In a darkened
room, place the card in front of the torch, so that narrow beams
of light come through the teeth of the comb. Hold a mirror in
the beams of light so that it reflects the light. Move the mirror
to a different angle. Predict what will happen to the angle of
the reflected light rays as the light hits the mirror.
- Have
students describe a mirror image of themselves. What size are
you in the mirror? Where is your right side in the mirror? How
does the reflection of light cause a reverse image?
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Activity
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Class
Periods Needed to Complete
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Teaching
Approaches to Consider
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Features
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5.
Bending Light
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one
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Teacher
demonstration
Students
working in pairs or small groups
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Sidebar:
The Archerfish
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Teaching
Ideas
- A
container of water with a few drops of milk makes a great medium
to visualize the refraction of a laser pointer beam. It will also
make the point that, as the beam passes out of the container and
into the air, it bends again as seen by the position of the laser
dot on the wall. Does the angle of refraction get even larger,
or does it correct itself when it leaves the jar?
- A
simple spoon can serve as a concave/convex mirror for further
investigation of refraction. The scoop of the spoon is concave,
the back, convex. How does a concave mirror distort, or change,
the image? Predict how the convex mirror will distort the image.
- Use
a large fish tank of clean water to create a refraction game.
Drop several waterproof items in the tank and have students retrieve
each item. Explain that it will be harder than it sounds because
the item will not be where their eyes tell them it will be. Have
students explain why, using the term refraction.
- Teach
students a standard magic trick – the disappearing penny.
Place a penny under a clear drinking glass. Pour water into the
glass. The penny will appear to vanish when looking through the
side of the glass. (It is still visible from above the glass.)
Invite students to explain how the trick works using the term
refraction.
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Visible light is the part of the electromagnetic spectrum that is visible
to the human eye. The EM spectrum is the range of different types of radiated,
or transmitted, energy. Besides visible light, other parts of the EM spectrum
include x-rays, UV rays, and infared.
(see http://amazing-space.stsci.edu/light/ems-frames.html)
Scientists
have learned much about the nature of light in the past few centuries.
We know that white light is actually made of all the colors together.
A prism can be used to separate white light into the rainbow that forms
it. Colors can be seen well in white light because an object that is red,
for example, absorbs all colors except red, which it reflects and the
eye detects. Objects that absorb all light appear black.
Light can
be both a cause and an effect, a producer and a product. For example,
extreme heat can create light, such as in a chemical reaction. And light
causes photosynthesis, causing plants to grow. Photoconductors produce
electricity, while electricity can heat a glass bulb filament enough to
create light.
Some ways
that light behaves can be explained by the fact that it is made of particles.
Other behaviors are better explained when thinking of light as waves.
In 1690, Dutch scientist Christian Huygens tried to prove that light comes
in waves. Soon afterward, Sir Isaac Newton experimented proving that light
comes in particles. At that time, the scientific world believed that the
same energy could not coexist as both waves and particles. Therefore,
most scientists dismissed Huygens' theories.
More than
100 years later, however, several scientists did more to prove Huygens'
idea. They used different experiments to show light moving in waves. One
property of light proving the wave theory is refraction, or how light
moves around an object. Some experiments illustrated that light moves
much like waves in water do.
As in water
or sound waves, light waves have specific properties. Waves have crests
(high points) and troughs (low points). A wavelength, measured from crest
to crest, determines the color of the light. Frequency, or the amount
of waves going through a fixed point per second, establishes the type
of EM wave, such as visible light or radio waves.
Seemingly disproving the wave theory, Sir Isaac Newton stated in 1704
that light comes in tiny particles. A respected scientist, Newton used
convincing experiments and calculations. In 1905, Albert Einstein upheld
Newton's theory by showing that light travels as little bundles of energy
he called photons. Einstein was able to explain how any EM energy
behaves both as a wave and as a stream of photons.
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