Determination of UVB absorbance of sunscreens and zinc oxide through UVB irradiance sensing.

Date

4-2011

Degree

Bachelor of Science in Applied Physics

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Emmanuel A. Florido

Abstract

The relationship of the relative ultraviolet (UVB) light absorbance to other intrinsic properties of various substances was investigated. This study included the measurement of a) the relative UVB absorbance of 14 samples of sunscreen lotion for different photoprotective ratings, ranging from sun protection factor (SPF) 15 to SPF 60, and b) the relative UVB absorbance of zinc oxide (ZnO)-plain lotion mixture for different ZnO mass concentrations (6%, 12% 25% and 50%). The samples were applied on a microscope glass slide and irradiated by sunlight. The UVB content of the transmitted light was measured using a UVB sensor. The relative UVB absorbance of the glass slide and the sample was determined by computing the percent difference between the incident and transmitted UVB irradiance. The result of the absorbance measurement showed that UVB absorbance was high for higher SPF-labeled sunscreens. It was observed however, that the UVB absorbance among different SPF-labeled sunscreens was not statistically significant. This suggested that SPF15 sunscreens can already give adequate protection from UVB. On the other hand, the result of the absorbance measurement for the ZnO-plain lotion mixture showed that the UVB absorbance was generally higher for higher mass concentration. This particular result was consistent with the results of previous work that sunscreens with higher zinc oxide concentrations provide better sun protection from ambient UVB radiation.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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