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Special Frisbees Detect Ultraviolet Radiation
This experiment will help students understand that ultraviolet radiation is
present in natural outdoor light and that the intensity of the light varies
with season and time of day.
The energy from the sun includes not only visible light but also wavelengths
longer (infrared) and shorter (ultraviolet) than visible light. The wavelengths
of visible light increase from the blue to the red end of the spectrum. Shorter
than blue are wavelengths referred to as ultraviolet (UV). Ultra means beyond,
so ultraviolet means beyond (actually, shorter than) violet.
The amount of UV radiation reaching the earth's surface depends on the distance
it travels through the atmosphere. During morning hours, UV radiation must travel
through more of the earth's atmosphere because the sun is lower on the horizon.
At noon the rays travel a shorter distance through the atmosphere because the
sun is more directly overhead.
If you would like to extend this activity into an inquiry-based laboratory
for your students, a guide has been included along with a sample lab report
- Students will understand that ultraviolet radiation is present in natural
- Students will be able to demonstrate that UV radiation can be blocked or
filtered by various substances.
- Students will be able to explain that the amount of UV radiation varies
with time of day.
Alignment to National Standards
National Science Education Standards
- Physical Science, Transfer of Energy, Grades 5 to 8, pg. 155, Item #6:
"The sun is a major source of energy for changes on the earth's surface.
The sun loses energy by emitting light. A tiny fraction of that light reaches
the earth, transferring energy from the sun to the earth. The sun's energy
arrives as light with a range of wavelengths, consisting of visible light,
infrared, and ultraviolet radiation."
- Physical Science, Interactions of Energy and Matter, Grades 9 to 12, pg.
180, Item #1: "Waves, including sound and seismic waves, waves on water,
and light waves, have energy and can transfer energy when they interact with
- Physical Science, Interactions of Matter and Energy, Grades 9 to 12, pg.
180, Item #2: "Electromagnetic waves result when a charged object is
accelerated or decelerated. Electromagnetic waves include radio waves (the
longest wavelength), microwaves, infrared radiation (radiant heat), visible
light, ultraviolet radiation, x-rays, and gamma rays. The energy of electromagnetic
waves is carried in packets whose magnitude is inversely proportional to the
Benchmarks for Science Literacy, Project 2061, AAAS
- The Physical Setting, Motion, Grades 6 to 8, pg. 90, Item #1. "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."
- The Physical Setting, Motion, Grades 6 to 8, pg. 90, Item #5. "Human
eyes respond to only a narrow range of wavelengths of electromagnetic radiationvisible
light. Differences of wavelength within that range are perceived as differences
- Grade level: 5 to 9
Time for this activity is highly variable and dependent on the level of sunlight
and type of test selected. This activity would serve well as a scientific
inquiry project for even younger students. Allow students to work in teams,
have them select an experiment to run on the Frisbees (plastic shields, sunscreen,
etc.), decide how to do it, and carry it out. This will take at least two
periods. Simpler demonstration activities will take correspondingly less time.
- 5 UV-sensitive Frisbees (small), or one large one cut up into pieces
- Squares of plastic of various thickness (1/32 to 1/2" thick). Plastic
scraps may be obtained at hardware stores or glass companies.
- Black light may be used on cloudy days
Note: Frisbees are manufactured by Wham-O Manufacturing Co. (www.wham-o.com)
and can be found in many local toy stores.
Note: At the end of this activity write-up, there are suggestions for teachers
wishing to use a more inquiry-based approach. A sample student lab write-up
is also included.
- Place Frisbees on tray.
- Leave one Frisbee uncovered. Cover each of the others with plastic sheets
of various thickness.
- Make a data sheet similar to the one suggested at the end of this activity.
- Cover the entire tray with a cloth to block all light. Carry the tray outside
and place in direct sunlight.
- Remove cover in sunlight and fill out data sheet.
Observations and Questions
- Did the Frisbees change color when exposed to normal room lighting? (Not
usually.) Why or why not? (Because there is very little UV radiation in indoor
- What happened to the color of the Frisbees in sunlight? (They turned pink.)
Why do you think these results occurred? (The UV light causes a photochemical
reaction that causes the Frisbee to turn pink.)
- What effect did the various pieces of plastic have upon the color of the
Frisbees? (The Frisbees did not turn color.) Why do you think these results
occurred? (Probably the plastic blocked the UV light so the photochemical
reaction was unable to occur.)
- Relate this activity to the interaction of ozone and UV radiation in the
stratosphere. (The thinner the layer of ozone, the more UV radiation that
will get through. For example, a typical amount of ozone is 300 Dobson units.
If all the ozone in a column were to be compressed to standard temperature
and pressure (STP) (0 deg C and 1 atmosphere pressure) and spread out evenly
over the area, it would form a slab approximately 3 mm thick. One Dobson Unit
(DU) is defined to be 0.01 mm thickness at STP. The unit is named after G.M.B.
Dobson, one of the first scientists to investigate atmospheric ozone (~1920
- 1960). He designed the 'Dobson Spectrometer' - the standard instrument used
to measure ozone from the ground. The Dobson spectrometer measures the intensity
of solar UV radiation at four wavelengths, two of which are absorbed by ozone
and two of which are not. In the ozone "hole," the thickness has
dropped to as low as 100 DU.)
- Test the effectiveness of different types of filters, such as different
types of plastics (acrylic, Lucite, Plexiglas), glass (you can use glass slides;
stack a number together for different thicknesses), water, different types
of cloth, sunscreens with different SPF numbers and/or different brands, different
types of artificial lights (fluorescent, incandescent, heat lamp, black lights,
- Test the Frisbees at different times during the day, under different degrees
of cloud cover, and at different seasons. Can you relate the amount of UV
radiation to different amounts of atmosphere that solar radiation travels
Sample Data Chart
Number of sheets of glass, plastic, sunglasses, or
type of sunscreen
- As noted above, this would serve well as a scientific inquiry task and
would allow the teacher to assess the students' understanding of UV effects
as well as their ability to design and conduct a simple, independent experiment.
Modifications for Alternative Learners
- No modifications should be necessary.
Notes to Teacher
Suggestions to implement this activity through an inquiry approach
- Collect an assortment of substances such as: sunscreens and tanning lotions,
lip balm and/or face creams, UV protective additive for paint (hardware stores
should carry these), sheets of various plastic films (food wrap, mylar, acetate),
and small pieces of clear acrylic and polycarbonate.
- To avoid reliance on clear, sunny days as your UV source, you may use commercial
UV lamps of various types (many are sold as 'mineral-lights' and are used
to identify fluorescent minerals), but whenever using UV lamps, use great
caution in limiting student exposure to the lamps.
- Use any acceptable form of a lab write-up or oral lab report. Students should
have the opportunity to explain what the question is and why it's important,
describe in detail their experimental procedure, report their results in text
and graphic form (graphs, tables), and explain how the data they collected
answers the question. An example lab write-up format (intended for upper-level
students) is appended.
Example Lab Report Format
In this class we will frequently be doing labs that you design and carry out
on your own. For these labs, you will turn in a report, either on paper or on
disk (your choice) that follows the following format:
- TITLE: The title should specifically describe what the lab is about ("The
effect of insecticides on plant growth," not "Chemicals and plants").
- INTRODUCTION: Tell the reader why you are doing the study. Give enough background
information so the reader will understand why the subject and the study is
important. Tell the reader what you are trying to figure out in the form of
a clear, logical, and answerable question.
- MATERIALS: List all the supplies that you used so someone else could use
exactly the same materials when repeating your study.
- PROCEDURE: Pretend your lab is like a recipe and that you are writing for
a reader not as smart as you. You have to describe exactly what to do and
how to do it or the reader will probably mess it up. Procedures are best written
in a numbered list (step 1, step 2, etc.) rather than in paragraph form, but
if you like the paragraph form and can write very clearly, you may use it.
If you've done it correctly, a younger student ought to be able to follow
your instructions. Drawings or diagrams are often helpful. Be sure to identify
CONTROL treatments and REPLICATES clearly in your procedure.
- RESULTS: Data can take many forms, but it all needs to be clearly shown
to the reader. You may use drawings, tables, or graphs, depending on what
you are trying to show, but all have to be very well labeled, with titles
and all units shown. You must also write in paragraph form what you found.
This is where you draw the reader's attention to the most important or useful
parts of your data. We will discuss these issues further in class.
- DISCUSSION AND CONCLUSION: This is the heart of the lab! Plan to spend LOTS
of time on this section! This section should be written in paragraph form,
not in a list. There are several parts to a good discussion section:
a. Summarize why you did the lab and how you did it.
b. Summarize what you found.
c. Relate your findings specifically back to your purpose or question. Did
you fulfill the purpose, answer the question? (It's totally OK if the answer
is no; many experiments don't turn out to be what we expect them to be.) Either
way, explain why.
d. Discuss sources of error: These are things that you couldn't controlfaulty
equipment, limits on time or resources, other things you didn't plan on. Don't
cop-out by just reporting that you messed up.
e. If I wanted to pursue this research, what would you recommend that I do
next? Leave me with a sense of where the research would go from here.
When you're finished with the activity, click on To Student
Guide or Back to Activities List at the top of the page.