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.

1. Spray Vs. Lotion: The Effect
of Sunblock on UVA and
UVB
F. Allaire, A. Suenobu, L. Wells
PHYS 399 Summer ’09

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

10. Experimental Design
Lotion
Control
Spray

11. Experimental Design
UVA and UVB
Probes and the
LabQuest
handheld device.

12. The application of sunblock
Lotion
Spray

13. Setting up in the sun….

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.

15. Variables that could
affect results…
Cloudy
day!

16. Variables that could
affect results…
The amount of spray:
Two pumps of the
spray bottle from the
same distance away
from plastic!!

17. Variables that could
affect results…
The amount of lotion:
Small amount each
time on fingertips
applied with the
same pressure onto
plastic.

21. UVA:
Comparing spray, lotion and control

22. UVA:
Comparing spray and lotion

23. UVB:
Comparing spray, lotion and control

24. UVB:
Comparing spray, lotion and control

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.