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March 2015
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Do you see what I see? Light, sight, and natural selection
Lesson 4: What are color and light?
I. Overview Students continue to investigate how the environment affects perception by gaining a deeper
understanding of the physical properties of light. The lesson begins with an animated video that
contextualizes color in the electromagnetic spectrum and light at a physical phenomenon. Students use
spectrophotometers to explore the emission, reflection, absorption, and transmission of light from
various light sources and objects. Interpretation of these results is supported with a video of typical
results, helping students integrate their observations with knowledge of the RBG (Red-Blue-Green, or
additive) color model.
Connections to the driving question In Lesson 1, students built an initial model of color perception and started an investigation. In this
lesson, students continue collecting evidence on the physical properties of light and additive/subtractive
color models which can be used later to revise their model in Lesson 5.
Connections to previous lesson In the previous lesson, students sorted colorful candies under different colored lights in order to observe
the effect that the environment can have on the perception of color. This lesson further develops the
investigation with a deeper, scientific understanding of the mechanisms behind how light interacts with
the environment, leading to changes in color perception.
II. Standards
National Science Education Standards
Abilities necessary to do scientific inquiry. Identify questions and concepts that guide scientific
investigation (9-12 A: 1/1).
Abilities necessary to do scientific inquiry. Use technology and mathematics to improve
investigations and communications (9-12 A: 1/3).
Understandings about scientific inquiry. Scientists rely on technology to enhance the gathering
and manipulation of data… (9-12 A: 2/3).
Benchmarks for Science Literacy
Light from the sun is made up of a mixture of many different colors of light, even though to the
eye the light looks almost white. Other things that give off or reflect light have a different mix of
colors. 4F/M1
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Human eyes respond to only a narrow range of wavelengths of electromagnetic waves—visible
light. Differences of wavelength within that range are perceived as differences of color. 4F/M5
There are a great variety of electromagnetic waves: radio waves, microwaves, infrared waves,
visible light, ultraviolet rays, X-rays, and gamma rays. These wavelengths vary from radio waves,
the longest, to gamma rays, the shortest. 4F/M8
Next Generation Science Standards
Science and Engineering Practices
o Developing and Using Models
o Analyzing and Interpreting Data
o Constructing Explanations and Designing Solutions
Disciplinary Core Ideas
o ETS2.A: Interdependence of Science, Engineering, and Technology
o PS3.A: Definitions of Energy
o PS4.B: Electromagnetic Radiation
o PS4.C: Information Technologies and Instrumentation
Crosscutting Concepts
o Energy and Matter
III. Learning Objectives
Learning Objective Assessment Criteria Location in Lesson
Gain experience using
different types of
scientific models
Students compare the subtractive and additive color
models, especially using the latter to interpret
results of the investigation.
Light Video Part 2,
Closing of Lesson,
Student Packet:
Summary Question 4
Collect, analyze, and
interpret data within an
investigation
Students compare their predictions to the observed
results during and after the investigation.
Closing of Lesson,
Student Packet:
Summary Questions
Practice constructing a
scientific explanation
Students use their knowledge gained in Lesson 4 to
create an explanation for phenomena observed in
Lesson 3 (Colorful Candy Activity)
Closing of Lesson,
Assessments
Describe how science,
engineering, and
technology are
interdependent
Students use the spectrophotometer as an example
of engineered technology that can further scientific
inquiry.
Closing of Lesson,
Student Packet:
Summary Question 1
Understand how
wavelengths, light, and
Students describe the electromagnetic spectrum,
the different types of radiation and light, and their
Student Packet: Pre-
Investigation
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energy are related relationship to wavelengths and energy. Questions
Describe the
electromagnetic and
visible spectrums
Students can interpret a diagram of the
electromagnetic spectrum with the visible spectrum.
Student Packet: Pre-
Investigation
Questions
Define key terms used
to describe the physical
properties of light
Clear, concise, accurate definitions of the following
terms provided: electromagnetic radiation, the
visible spectrum, wavelength, absorption, reflection,
transmission, emission
Student Packet: Pre-
Investigation
Questions
Account for how the
human visual system
can interpret a wide
variety of colors.
Cites examples based on the RGB (additive) color
model and unequal activation of a combination of
the three cone types to produce many possible
combinations of colors
Verbal questions in
Activity 2 of the
demonstration
Distinguish between the
physiological and optical
interpretations of light
Example from the demonstration is described in
which a color that was observed did not correspond
to the wavelength of a solitary peak on the spectrum
Student Packet:
Summary Questions
3, 4
Interpret a light
intensity spectrum
Accurately sketch and describe the peaks that are
observed
Graphs in the Student
Packet; Activity 1
discussion questions
IV. Adaptations/Accommodations Depending on resources or time, this lesson can be structured in different ways. This lesson is structured
as student-driven instructor demonstration, in which student ask questions and make suggestions to an
instructor who uses the spectrophotometer and displays the results on an overhead projector.
Individual students can also be asked to come up and demonstrate their predictions. However, if
multiple spectrophotometers are available, it is highly recommended that student groups are formed so
that students can directly manipulate and experiment with the spectrophotometers and the materials.
Throughout the lesson, it is assumed that one lightbulb is used per lamp. However, if resources are
limited, use multiple bulbs in one lamp by switching them out. Use caution because bulbs become hot.
This lesson was developed and tested using Vernier SpectroVisPlus spectrophotometers, although the
lesson can be adapted to any appropriate spectrophotometer.
Safety Consumption of the dyed water should be strictly prohibited. Although the dyes used during this activity
are deemed safe for use in foods by the Food and Drug Administration, food dyes may cause allergic
reactions (sometimes severe) in some students.
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The desk lamps and bulbs become hot over time while in use, so handle these with care. In addition,
fluorescent light bulbs contain trace amounts of mercury and should be disposed of properly.
V. Timeframe for lesson
Opening of Lesson
Light Video Part 1 – 10 minutes
Main Part of Lesson
Activity 1: Monochromatic/White Light Emission interactive demonstration – 10 minutes
o Activity 1a: Monochromatic (Colored Light) Emission
o Activity 1b: White Light Emission
Activity 2: Emission from Multiple Lights interactive demonstration – 15 minutes
o Activity 2a: Emission from Multiple (Two) Lights
o Activity 2b: Emission from Multiple (Three) Lights
Activity 3: Reflection interactive demonstration – 20 minutes
Activity 4: Transmission vs. Absorption interactive demonstration – 15 minutes
Conclusion of Lesson
Light Video Part 2 – 10 minutes
Summary discussion – 10 minutes
VI. Advance prep and materials
Opening of Lesson
Materials:
“What are Color and Light? (Light Video: Part 1)” (available online at
http://neuron.illinois.edu/light-video-part-1)
Overhead projector connected to computer
Spectrophotometer, see details in U1_L4_TeacherResource_SpectrophotometerInstructions.docx
Optional: Light and Color Models, Teacher presentation slides
(U1_L4_TeacherSlides_LightAndColorModels.pptx)
Student Packet (U1_L4_StudentPacket_ColorInvestigations.docx)
Extra Color Investigation Sheet (U1_L4_StudentSheet_ExtraColorInvestigationSheet.docx)
Preparation:
Download the video and test playing it via the classroom computer
Test opening the presentation slides, if needed
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Set up spectrophotometer, see details in
U1_L4_TeacherResource_SpectrophotometerInstructions.docx
Make enough copies of the Student Packet for each student.
Make copies of the Extra Color Investigation Sheet, as necessary.
Activity 1: Monochromatic/White Light Emission interactive demonstration
Materials:
Spectrophotometer (from Opening of Lesson)
Student Packet (from Opening of Lesson)
Optional: Sample Spectra Results (U1_L4_TeacherSupplement_SpectraResults.docx)
Desk lamps, at least three, or one for each different-colored light
o Note: Alternatively, light bulbs can be switched out of a single lamp
Assorted monochromatic fluorescent light bulbs (include green, blue, red, especially; include
purple and yellow if possible)
1 full-spectrum (white) fluorescent light bulb
Preparation:
See the Spectrophotometer Instructions document for spectrophotometer set up
(U1_L4_TeacherResource_SpectrophotometerInstructions.docx)
Set up bulbs in the lamps as necessary
o Ideally, put one bulb in each lamp
o For this activity, have at least one white bulb and one color bulb
Run through the demonstrations to observe the resulting spectra ahead of time. A document
called U1_L4_TeacherSupplement_SpectraResults.docx has been created to provide you with
some sample results. It may be helpful to review this document ahead of time.
Activity 2: Emission from Multiple Lights interactive demonstration
Materials:
1 piece of white paper
Other materials same as Activity 1
Preparation:
Preparation same as Activity 1.
Run through the demonstrations to observe the resulting spectra ahead of time. A document
called U1_L4_TeacherSupplement_SpectraResults.docx has been created to provide you with
some sample results. It may be helpful to review this document ahead of time.
Activity 3: Reflection interactive demonstration
Materials:
An assortment of some or all of the following
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o Colorful candies (large, matte if possible)
o Shiny tree ornaments
o Colored translucent plastic, such as cellophane
o Colored pieces of paper
Other materials same as Activity 1
Preparation
Preparation similar to Activity 1.
Run through the demonstrations to observe the resulting spectra ahead of time. A document
called U1_L4_TeacherSupplement_SpectraResults.docx has been created to provide you with
some sample results. It may be helpful to review this document ahead of time.
Activity 4: Transmission vs. Absorption interactive demonstration
Materials:
Plastic Cuvettes (Model #: CUV)
4 beakers (50 ml or larger)
Plastic droppers
Red, blue, green, and yellow liquid food coloring (McCormick Assorted Food Color and Egg Dye)
Water (40 ml per beaker)
Spectrophotometer (see Opening of Lesson)
Preparation:
Set up spectrophotometer, see details in
U1_L4_TeacherResource_SpectrophotometerInstructions.docx
Fill each of the beakers with 40 ml of water
Add food coloring to beakers. (These amounts of food coloring will insure that light will be both
absorbed and transmitted at the expected wavelengths. Water dyed too lightly will transmit too
much light, and water dyed too heavily will absorb the majority of the light.)
o 10–15 drops of red food coloring in the first beaker
o 3 drops of green food coloring in the second beaker
o 4 drops of blue food coloring in the third beaker
o 3–4 drops of yellow food coloring in the final beaker
Run through the demonstrations to observe the resulting spectra ahead of time. A document
called U1_L4_TeacherSupplement_SpectraResults.docx has been created to provide you with
some sample results. It may be helpful to review this document ahead of time.
Closing of Lesson
Materials:
“Where does color come from? (Light Video: Part 2)” (available online at
http://neuron.illinois.edu/light-video-part-2)
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Copies of the Student Packets titled “Color Investigations” (students already have this)
Answer key for “Color Investigations” (U1_L4_StudentPacket_ColorInvestigations_Answers.docx)
Slides with images of light and color models (U1_L4_TeacherSlides_LightAndColorModels.pptx)
Preparation:
Download the video and test it on classroom computer/projector
Homework and Assessment
Scientific Explanation (U1_L4_Assessment_ScientificExplanation.docx)
VII. Resources and references
Resources
The materials for this lesson can be downloaded for free from the Project NEURON website:
http://neuron.illinois.edu/do-you-see-what-i-see/lesson-4
For background science knowledge, see
U1_L4_TeacherResource_BackgroundScienceKnowledge.docx
For examples of results from the experiment, see
U1_L4_TeacherSupplement_SpectraResults.docx
References
Ramadas, J., & Driver, R. (1989). Aspects of secondary students' ideas about light. Leeds, UK:
University of Leeds, Centre for Studies in Science and Mathematics Education.
The Electromagnetic (EM) and Human Visible Spectra. Retrieved from http://www.antonine-
education.co.uk/physics_gcse/Unit_1/Topic_5/topic_5_what_are_the_uses_and_ha.htm
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VIII. Lesson Implementation
Opening of Lesson Remind students that they are investigating factors and variables that affect color perception. In the
previous lesson, students observed in the colorful candy activity that environmental light changes the
perception of colorful candies. Now they will investigate light and color with a special instrument to
understand the mechanisms of how color, a perceived quality of light, interact with the environment.
Ask students some questions or refer to their initial models of color perception to uncover their current
understanding of the physical characteristics of light.
Have you studied light in a physics class?
What do you already know about light?
Teacher Pedagogical Content Knowledge Revealing students’ preconceptions about light is important for two reasons. First, it
helps students consider what they already know about the topic. Second, it provides a
means of assessment so that the lesson may be modified to meet students’ needs
accordingly.
If students did not already watch “What are Color and Light? (Light Video: Part 1)”, allow them to do so
in class (video is approximately 5.5 minutes long).
After the video, ask students some questions to encourage their reflection on the content of the video.
Project or show the electromagnetic spectrum diagram (U1_L4_TeacherResource_DiagramSlides.pptx)
for students to examine or refer to as they answer questions.
These questions are also listed in the Student Packet (U1_L4_StudentPacket_ColorInvestigations.docx),
so students can record their answers. Suggested answers are available in the Answer Sheet
(U1_L4_StudentPacket_ColorInvestigations_ANSWERS.docx).
In your own words, what is the electromagnetic (EM) spectrum?
What is the visible spectrum, and how is it different than the EM spectrum?
What is a wavelength?
What type of light is invisible to humans?
What is the relationship between wavelength and energy?
Why do people wear sunscreen or lead vests at the dentist’s office?
Describe the following terms regarding light, using your own words:
o Emission
o Reflection
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o Absorption
o Transmission
To begin the investigation, introduce students to the equipment that will be used.
How do scientists measure different wavelengths?
What are spectrophotometers?
o They are instruments that measure energy wavelengths (e.g., UV and visible light). In
this case the spectrophotometers will only show measurements from the visible
spectrum.
If students are unfamiliar with the instrument, show them the different parts and the graph output.
Review the following parts of the graph output so students can make their predictions.
The graph only shows the visible spectrum
The x-axis shows wavelength from short to long waves
The y-axis shows relative intensity
Next, explain that students will be directing the investigation, but they must make a series of prediction
statements to test their ideas. This is important so that students can record and compare their previous
knowledge and assumptions to what they learn as they progress in the investigation.
Student Misconceptions It is important to note that the only different between the waves of the visible
spectrum and the rest of the electromagnetic spectrum is the amount of energy the
waves carry. Students may attribute actual physical differences to waves of the visible
spectrum, such that they are intrinsically “colorful.” However, by the end of this lesson
and unit, students should appreciate that the reason this range is called the visible
spectrum is because it is the small range of light that human vision has evolved to
detect in their environment on Earth and that humans perceive as “visible.” Other
animals have a different “visible spectrum” and may see a wider or shorter range of
light (discussed more in Lesson 7). Ultimately, color is in our heads, not in the light!
Teacher Content Knowledge The spectrophotometer is a device used to measure how much light something, like a
light bulb, emits at different wavelengths within the visual spectrum when used in
conjunction with a portable optical probe that fits into the cuvette chamber.
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The Student Packet explains the Prediction Statement Protocol below. Pass out the Student Packet and
review this with students before beginning the investigation.
How to make a Prediction Statement The basic formula is an “If…then…” statement that contains a mechanism and a prediction.
If [mechanism], then [prediction].
The mechanism is the scientifically based reason (to the best of your knowledge) of what you think is happening.
The prediction is a directly observable event that you think you will see. Example: “If the blue light bulb is emitting blue light, then I predict that the graph will only show a peak
near the wavelengths associated with the color blue.”
To demonstrate the spectrophotometer and the prediction, ask students to share out loud:
What happens to the graph when the probe is moved farther from the light source?
What are possible predictions?
o This is usually easier for students to start with.
o Example prediction: The spectrum profile will be reduced along the y-axis, which shows
intensity.
What are possible mechanisms?
o Typically harder for students, but it’s basically why they think the prediction will happen.
o Example mechanism: The light will be less intense, because less light will enter the probe
if it is further away from the source.
What is your prediction statement (all together)?
o Example: If less light enters the probe when it is further away from the light source, then
the light will be less intense, and I predict that the graph will be reduced along the y-axis,
which shows intensity of light.
Test the prediction statements by showing students what happens to the graph when the probe is
moved farther from the light source. The general profile of the spectrum should remain the same, but
everything should be scaled. This reflects the fact that relative intensity is being plotted on the y-axis.
The software should readjust the scale automatically after a few seconds.
Main Part of Lesson The activities below are presented as interactive demonstrations with one spectrophotometer but can
be adapted if more resources are available (see Section IV Adaptations/Accommodations).
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Activity 1a: Monochromatic (Colored Light) Emission
Tell students they will first investigate emission from a colored light. If different colors of lightbulbs are
available, ask students which light they’d like to look at first and allow them to come to a consensus.
Then allow students to spend a moment to make a prediction statement and draw a prediction graph
(Steps 1 and 2 on the Student Packet).
Note: Lightbulbs of different colors can be tested, but students must chose to make a prediction and
collect data on at least one. If students would like to record additional data, extra blank graph sheets for
printing are available (U1_L4_TeacherResource_ExtraColorInvestigationSheet.docx).
Proceed to dim the room lights, and turn on a desk lamp with a colored light bulb. Point the
spectrophotometer probe at the bulb, and project the resulting spectrum generated by LoggerPro. See
the sample spectra results (U1_L4_TeacherSupplement_SpectraResults.docx) for examples of various
graph outputs.
Ask students to interpret the graph and to explain the significance of the observed peak. They can also
write any observations and questions as part of Step 5 on the Student Packet and share them with the
rest of the class.
Teacher Pedagogical Content Knowledge By having students record their predictions, they become more engaged in the activity.
If predictions are made aloud in the class, only a few students will be able to voice
their thoughts. The rest of the class may not have committed to a prediction. If all
students are asked to write their predictions, then they commit to their thinking. This
sets students up to look for evidence to support their predictions during the
demonstration, or it provides a situation in which students must modify their original
thinking.
Allow students to suggest other color emissions they want to test and repeat the demonstration with a
few other monochromatic light bulbs (red, green, yellow, purple). Some bulbs, such as the yellow (which
shows peaks in the yellow, red, and green wavelengths) show confusing results.
Avoid providing students with an answer and encourage them to keep these confusing results in mind as
they continue the investigation. At the end of the lesson, they will have the opportunity to create a
scientific explanation using the RGB color model to explain different phenomena.
Teacher Pedagogical Knowledge The think-pair-share technique can be used throughout this lesson in order to engage
more students by a single question. First, all students are asked to think individually.
Then students pair with a neighboring student and share their responses. Remind
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students to discuss similarities and differences in their responses. This allows the
teacher to listen to conversations and assess multiple students at once.
Activity 1b: White Light Emission
As a final run, repeat the demonstration with a white (full-spectrum) light bulb. Ask students to make
prediction statements and graphs as before. Ask the following questions to help students analyze their
results.
What sort of spectrum did you expect the white bulb to generate?
o Because white light is made up of all the colors, we would expect the intensity of all
wavelengths to be fairly high.
Where in the visible spectrum is the white light bulb generating the most energy?
o This will depend on the type of fluorescent white light bulb being used, but it will
correspond to the highest peak.
The white bulb may be confusing to students because it is not actually “full spectrum.” If possible,
compare the results for the white bulb to the results when the probe is in sunlight. (These results are
discussed in the Closing of the Lesson and Light Video: Part 2 at the end of the lesson).
Activity 2a: Emission from Multiple (Two) Lights
Introduce the next activity and introduce the concept of color mixing by asking students
Where do you suppose other colors, like grey, brown, maroon, etc., come from?
What do you remember about color mixing in earlier grades?
o “Primary” colors mix to form the “secondary” colors.
o Most students will identify the primary colors as “blue, red and yellow” and the
secondary colors as “purple, orange and green.”
o Students will likely be more familiar with the subtractive model (above) than the additive
or RGB color model.
Tell students they will now investigate what happens when light mixes. Write the following
combinations on the whiteboard and ask students to pick one and make a prediction of what the
spectrum will be on the graph.
Red + Green
Blue + Red
Blue + Green
After students make their predictions, dim the overhead lights and shine two different light bulbs (of
one of the combinations above) at a central point, such as onto a piece of white paper. Position the
probe so that it is at this central point, facing each of the two light bulbs equally.
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Each color combination will mix to form a new color on the white sheet of paper. However, the
spectrophotometer will only show the original bulb colors as peaks!
Ask students who made predictions for the chosen bulb combination record their results. Go through
each combination, allowing students to record the results. Write down the resulting mixed color from
each combination on the board:
Red + Green = Yellow
Blue + Red = Magenta
Blue + Green = Cyan
Activity 2b: Emission from Multiple (Three) Lights
Lastly, prepare to use a combination of the red, green, and blue bulbs simultaneously. Again, ask
students to write a prediction statement and graph of what color(s) they think the combined light will be
in the space provided for Activity 2b.
After predictions have been made, shine the three different light bulbs at a central point such as onto a
piece of white paper. Position the probe so that it is at this central point, facing each of the three light
bulbs equally.
The light at the point where all the colors mix will appear white. Add to the board:
Red + Green + Blue = White
Students will use this information later to discuss the RGB or additive color model.
Activity 3: Reflection
Introduce the activity by asking students
What else can happen to light if it doesn’t travel directly from a source to our eyes?
o Some of the light may contact and be redirected by some form of matter.
Show students the two sets of colored objects, assorted colorful candies and colorful ornaments, and
have students predict how these different objects could be used to illustrate differences in reflection.
Start by using a white light bulb and two different objects of the same color (such as a red candy and a
red ornament). Have some students chose one object and some students the other object. Give them
some time to write down their prediction statements.
Student Misconceptions Some students struggle with the idea that light reflects off of objects like the candy
(Ramadas & Driver, 1989). Students may think that light only reflects off of metallic
objects or mirrors because they look shiny.
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Using students’ ideas, carry out a short demonstration that illustrates how light is reflected. The room
lights will need to be dimmed as in previous demonstrations. Engage the whole class by asking how and
why they would like the light source positioned relative to the object and, in turn, how they would like
the probe positioned relative to both. Remember an objective in these demonstrations is to have the
probe catch as much of the reflected light from the object as possible.
Experiment with different sorts of orientations and distances, and have the students observe how the
reflected spectra change accordingly.
Teacher Pedagogical Content Knowledge The reflection of wavelengths off of certain surfaces, such as the candies, may be
difficult to detect with the light probe. Consider recording the spectrum of a surface,
such as the table top or desk, without an object as a control. Also, consider changing
the light source by going outside to use light from the Sun. The relatively higher
intensity light can produce results that are more easily detected. See
U1_L4_TeacherSupplement_SpectraResults.docx for sample results with additional
explanation.
Check for understanding. Ask students:
Based on what you have learned about optics, do the reflected spectra being generated make
sense to you? For example, if you shine white light on a green ornament, what wavelengths of
light would you expect to find on the reflected spectrum?
o The expectation would be that green would be the wavelength most prominently
reflected, while red and blue wavelengths would be most readily absorbed.
o If this is not what the associated reflected spectrum shows, ask the class what they think
accounts for the discrepancy.
Results are further discussed at the Closing of the Lesson, in the sample results provided in
U1_L4_TeacherSupplement_SpectraResults.docx, and in the Light Video Part 2.
Activity 4: Transmission vs. Absorption
Ask students to briefly review and summarize how light is emitted from a source (emission) and how it is
reflected off an object (reflection). Ask students:
Are any other ways in which light can interact with an object or substance before it reaches the
eye?
o Light can also pass through or be absorbed by some objects or substances (transmission
and absorption respectively).
This topic can also be introduced through a series of questions about panes of glass:
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If you were to hold a clear pane of glass up to a white light source, what would happen to the
light when it reached the pane of glass? What would be the color of the light on the side of the
pane opposite the light source?
o Since the light is passing through the glass (i.e. being transmitted through the glass), it
would remain white on the side opposite the light source.
What color would the light on the side of the pane opposite the light source be if the glass were
tinted red?
o Only the red light would be transmitted through the pane of glass.
What happens to the rest of the light?
o Much of the light in the non-red regions of the visual spectrum have been absorbed by
the glass. This is known as absorption.
The following demonstration uses different colored water and the spectrophotometer to demonstrate
the concepts of transmission and absorption. Give one of the plastic cuvettes to the students and have
them pass it around the class.
Explain that cuvettes are tools designed to hold liquid samples that are measured during experiments
using the spectrophotometer. By placing a cuvette into the spectrophotometer cuvette chamber,
absorbance and transmission of light can be measured.
Teacher Science Content Knowledge Transmission and absorption are useful as a measuring tool in scientific practices. For
example, quantities of a particular chemical substance can be measured using a
spectrophotometer. Known quantities of the substance are measures to create a
“standard curve” or relationship between absorbance and quantity. Then the
absorbance of samples with unknown quantities can be used to determine the
quantity. This basic technique is used in various chemical analyses.
Show students the beakers filled with the dyed water. Ask the class to identify each color (red, blue,
green, and yellow). Allow students some time to choose one of the colors and write a prediction
statement for the transmission and absorption spectrum graphs for their chosen beaker.
After the students have made their prediction statements and graphs, fill one cuvette for each of the
colors (students can be asked to do this over the sink to prevent any damage caused by spilling).
Consider using plastic droppers to avoid spills.
After the cuvettes have been filled, place each in the cuvette chamber one at a time and measure the
transmittance and absorbance for each color. (Refer back to the directions earlier in the lesson plan to
set up the software correctly.) Also note that the y-axis labels and scales change.
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Give students time to draw the results on their graphs and compare results. The following questions can
be used throughout the activity:
Where in the visible light spectrum does the liquid transmit the most amount of light?
Does the liquid only transmit light in the area of the spectrum that corresponds to the color
of the liquid? Why or why not?
Conclusion of Lesson Throughout the lesson, students have been gathering data on their initial perceptions and results from
their investigations. Now they will begin to answer questions that may have come up and begin to make
sense of the results they have seen.
Show the video “Where does color come from? (Light Video: Part 2), which is about 4.5 minutes long.
This video covers some of the confusing results that may have come up during the investigation and the
RGB color model. Specifically, this video covers:
Review of the spectrophotometer graph and axes
Differences between sunlight (true full spectrum) and white lightbulbs (false full spectrum)
Mixing colors of light that create colors that are not present on the spectrophotometer graph
Absorption and Transmission results
Review of color
After the video is completed, ask students to complete the discussion questions at the end of the
Student Packet. Encourage students to work in groups and compare results while they are making sense
of their investigations. Suggested answers and explanations are available in the answer document
(U1_L4_StudentPacket_ColorInvestigations_ANSWERS.docx.). While students are discussing their
answers, it may be useful to display images of the light and color models
(U1_L4_TeacherSlides_LightAndColorModels.pptx).
Ask students to save or copy any of their graphs, models, or question answers as evidence to revise their
Model of Perception in Lesson 5. Students can save their evidence in their folder or lab notebook.
Assessment
Student responses within the student packets will allow you to assess student achievement of the
learning goals for this lesson.
Additionally, an assessment for creating a scientific explanation is available. This assessment prompts
students to make a scientific explanation using the knowledge they gained in Lesson 4 about the
properties of light to explain the phenomena they saw in the colorful candy activity in Lesson 3.
