How+SPF+Affects+UV+Light+Penetration

Bharat M   Cary Academy ** ABSTRACT  ** The purpose of this experiment was to see whether the SPF of sunscreen affects the amount of UV light that penetrates it. After careful research and several observations, it was hypothesized that the higher SPF sunscreen the less UV light that would penetrate it. For the first three experiments the UV beads were placed on the table. There were three groups of beads and two beads in each group. Then the clear plastic wrap was stretched over each group. On one group, the 15 SPF sunscreen was smeared on the plastic wrap. On the second group, the 30 SPF sunscreen was smeared on the plastic wrap. Finally for the last group, the 50 SPF sunscreen was smeared on the plastic wrap. Then the UV light was shone on them for 1 minute. The UV light level was read and then the beads were set up the same way and the light was shone on them for 2 minutes. Lastly, the beads were set up and the light was shone on them for three minutes. For the first three experiments the UV beads covered by 15 and 30 SPF had the same UV light level or index and the 50 SPF beads had one less UV light level. For the last three experiments, the beads were set up the same way however instead of UV light the sun was used. The only difference in the results were that there was much more UV light collected when the sun was used.
 * HOW DOES THE SPF OF SUNSCREEN AFFECT THE AMOUNT OF UV LIGHT THAT PENETRATES IT **