This document summarizes an experiment that tested the effectiveness of sunblock lotion versus spray at protecting against UVA and UVB radiation. The experiment found no significant difference between a spray and lotion with the same SPF value. Both provided much better protection than a control with no sunblock. The purpose was to determine if application method (lotion vs spray) made a difference in sun protection. Extensions are proposed to further compare sunblock products and educate students on sun safety.
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Spray Vs Lotion V3.0
1. Spray Vs. Lotion: The Effect
of Sunblock on UVA and
UVB
F. Allaire, A. Suenobu, L. Wells
PHYS 399 Summer ’09
2.
3. Ultraviolet Radiation
Ultraviolet (UV) ultraviolet light is the light just
past the wavelength of the color violet on the
electromagnetic spectrum
UVA frequency ranges 400 - 320 nm
UVB frequency ranges 320 - 290 nm
UVC frequency ranges 290 - 100 nm (these
waves are absorbed completely by oxygen and
the ozone layer)
4. UVA –responsible for suntans and
premature aging of the skin and some cancers
UVB associated
with sunburns,
cataracts and
skin cancer
5. Why should we care about
UVA or UVB radiation?
Premature aging of the skin
Damaging the skin’s cellular DNA
Various forms of skin cancer
Eye damage including cataracts
Reddening of the skin and sunburn
6. Protective measures
Wear clothing with
Use sunglasses
Seek shade
Wear hats
SPF - Sun Protection Factor
The Skin Cancer Foundation maintains
that SPF’s of 15 or higher are necessary
for adequate protection.
7. Purpose
We know that sunscreen does protect.
The purpose of this experiment is to
determine if there is a difference in
effectiveness of protection from UVA and
UVB radiation between lotion or clear
spray-on sunblock.
8. Hypothesis
We predict that the lotion would provide
more protection than a clear spray-on
sunblock of the same SPF value.
9. Experimental Design
Independent variable: Lotion / Spray-
on Sunblock
Dependent variable: UVA, UVB
penetration (mW/m2)
Constants: Time of day, amount of
sunblock, length of time, SPF, brand,
multiple trials using same procedure for
each trial,
Control: Clear plastic –no sunblock
14. Data collection:
Day 1 – Ran 3 trials beginning at 9:55
am until completed.
Day 2 - Ran 3 trails beginning at 10:30
am until completed.
Averages were then made using all 6
trials for the 2 days the experiment was
conducted.
We worked carefully to keep all other
variables to a minimum.
25. Now for some numbers…
UVA UVB
Sunblock Irradiance % Total Irradiance % Total
(mW/m2) (mW/m2)
Control 7181.645 100 341.9 100
Lotion 159.673 0.022 13.8 0.040
Spray 272.284 0.038 13.3 0.039
26. Conclusions
Our hypothesis was refuted
Difference between spray/lotion and
control is significant
Difference between spray and lotion
seems insignificant
Wear something!
27. Extensions
Compare brands that have same SPF
value
Compare various SPF values
Compare time after application
Sunblock vs. SPF clothing/sun glasses
Effectiveness after water immersion
Amount of lotion/spray applied
Price vs. effectiveness
28. Student Research
Informal survey: How many students
wear sunblock?
Data from this experiment can be used
as a demo to introduce the topic.
Students will design and conduct
experiments based on extensions
provided in the conclusion.