Lab 1 - Molecules and Light William Byun Ilse Kruse Ana...

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Molecules and Light William Byun , Ilse Kruse, Ana Curran, Ryan Hawkins College of Chemistry, UC Berkeley, Berkeley, CA 94720 Spring 2010 Abstract- We examined the effectiveness of different concentrations of SPF 8 in a solution of 2- propanol. We determined the effectiveness of SPF 8 by measuring the extinction coefficients of the ingredients we used using the HP 8453 UV/visible light spectrometer . From the data we collected we created a Beers law plot that showed the absorption of each concentration as well as the effectiveness of blocking out the UV rays. We determined that the larger concentration of SPF in the 2-propanol solution was the most effective because it absorbed the most UV rays. Our extinction coefficient was (8.5 +- 0.2)*10 3 g/mL*cm To further investigate the relationship between SPF levels and UV absorption we used UV sensitive disks with different SPF levels to visually represent how efficiently the different levels of SPF held off the UV rays. This experiment proves that the higher the SPF, the higher the level of UV rays it can protect. 1. Introduction The purpose of this Molecules and Light lab is to try and determine the effectiveness of different concentrations and levels of SPF to absorb UV rays by comparing absorption rates and extinction coefficients of those different concentrations and levels. There are many sunscreens of different SPF levels ranging from SPF 8 to SPF 75. The common assumption is that the higher the concentration and level of SPF the sunscreen obtains the better it will absorb UV rays therefore providing better protection against UV rays. To test the effect of protection depending on different concentrations and levels of SPF, the absorbance capacity of different concentrations of SPF 8 were calculated at 310 nm. Ultra violet radiation is in the range of about 10nm to about 400 nm in the solar emission spectrum. The absorbency of SPF 8 is looked at in this lab at 310 nm because the compounds absorb the maximum amount of light within the 310 nm range. The sunscreen will protect the skin from sunburn because it absorbs the harmful UVB light that is present from 300 nm to 340 nm very well. (Douskey, 2010) A high absorption level of UV light leads to a greater extinction coefficient. The extinction coefficients of different levels and concentrations of SPF are compared to see the difference in absorbency levels and to determine which SPF level and concentration provides the best protection against harmful UV rays. SPF stands for sun protection factor and it only protects against UVB light. However, sunscreen’s ability to filter UVA light is another important component that is not accounted for in the lab. 2. Methods
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Lab 1 - Molecules and Light William Byun Ilse Kruse Ana...

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