Is there UV
light indoor
s?
What am I going to learn?
What light sources emit UV light?
Which sun
screen w
orks the
Does sunscreen actually protect us from UV light? b e s t ?
Can you get sunburned inside?
Where in the electromagnetic spectrum is UV light?
The Physics
of
Sunburn!
After a day in the sun, your skin is red, swollen, and
sensitive. But you used sunscreen! Granted, it was
only Sun Protection Factor (SPF) 5. You wonder if
you should have used a higher SPF. Would
sunscreen with a higher SPF block more harmful
rays from the sun? You decide to conduct an
experiment to test out your question and along the
way, answer some of the questions above!
What am I going to learn?
What light sources emit UV light?
Can you get sunburned inside?
Does sunscreen actually protect us from UV light?
Where in the electromagnetic spectrum is UV light?
After a day in the sun, your skin is red, swollen,
and sensitive. But you used sunscreen! Granted,
it was only Sun Protection Factor (SPF) 5. You
wonder if you should have used a higher SPF.
Would sunscreen with a higher SPF block more
harmful rays from the sun? Conduct an
experiment to test out your question using black
construction paper as a model for your skin!
Some questions to keep in mind during your
investigation are: What light sources emit UV
light? Can you get sunburned inside? Does
sunscreen actually protect us from UV light?
Where in the electromagnetic spectrum is UV
light?
Predictions
Answer these questions before doing the lab
1. What do you think will happen to the paper outside in the sun?
2. What do you think will happen to the paper inside?
3. What do you think sunscreen will do for the paper? How will the SPF of sunscreen
affect your outcome?
What you’ll need!
sun or UV light source
squares of black
construction paper
scissors
sunscreen of various
SPFs and one lotion with
no sunscreen
dark pen
What is SPF?
The SPF of a sunscreen is a multiplication
factor. Your skin already has a natural SPF,
and sunscreen strengthens that number.
If you can stay out in the sun for 15
minutes before your skin burns, using a
sunscreen with an SPF of 10 would allow
you to stay out in the sun for 10 times
longer (100 minutes), assuming the sun
doesn’t get stronger that day!
Let’s Experiment!
Steps:
1. Set aside one paper square and apply lotion with no sunscreen.
2. Coat the other squares of black construction paper with sunscreen. Rub
into paper until sunscreen absorbs
2. Label each square with the SPF you applied.
3. Place the paper squares outside in direct
sunlight. Weight them down with coins.
Why do I need to apply lotion with
no sunscreen to one square?
Lotion without any sunscreen will
act as our “experimental control,”
or point of reference. This means we
will check whether the sunscreen
protected our paper against the
paper with lotion (no SPF).
4. Repeat steps 1-5 with a second set of papers and place them indoors
under a regular light.
5. Leave the papers outside in the sun for at
least 5 hours. To increase the effect, collect
the papers at the end of the day and replace
them in the sun the next day.
Why do you think we are testing
paper inside as well as outside?
6. Last, repeat your experiment by covering the coated paper with glass
instead of coins or test various other oily substances (olive oil, vasoline, etc.)
on the paper.
8. At the end of the day, compare your squares to the
fade-o-meter below to determine how much they
faded. Record your observations in the chart on the
next page and graph them on the following page.
Results
Fade-O-Meter
1
2
3
4
SPF of lotion, or type of material
Lotion
(no SPF)
Notes:
5
6
7
8
Number on Fade-O-Meter
9
Fade-O-Meter number
Graph Your Data!
9
8
7
6
5
4
3
2
1
SPF
What happened?
Answer these questions after you do the lab
1. What did you observe happen to the paper outside and inside? How did this
compare to your predictions?
2. Is there a relationship between SPF and the amount the paper fades?
3. What are some sources of error that might have affected your experiment?
4. How well do you think the construction paper models your skin? How might it be
different from how sun affects your skin?
5. If you tested out other substances and materials, like glass, how could you use
the fading factor of your sunscreened squares to figure out the SPF of these other
materials?
Why did I see what I saw?
The electromagnetic (EM) spectrum, shown below, describes different
types of light. Light is referred to as an EM wave because it is made up
of both electric and magnetic waves moving together through space.
The EM spectrum is arranged by wavelength with longer wavelengths
to the left, shorter wavelengths to the right. We are most familiar with
visible light and all EM waves in the spectrum are types of light. Did you
know x-rays were a type of light?
Our eyes can only see the small portion of the EM spectrum called “visible
light” which includes all the colors of the rainbow. Everything else in the
spectrum is invisible to our eyes. For example, ultraviolet (UV) light is a part of
the spectrum we humans cannot see, but other animals can see UV light,
including bees, butterflies, and reindeer.. UV light has a smaller wavelength
than visible light, which is why it is to the right of visible light. Other types of
light we cannot see include radio waves, X-rays and microwaves.
Though we cannot see UV light, we can detect it in other ways. One way is
sunburn! When your skin turns red from sitting in the sun, it is detecting the
presence of UV rays. It also hurts! What are some ways we detect radio
waves? How about X-rays?