... http://www.epa.gov/sunwise/uvwhat.htmlãTotal Energy depends on many factors including the intensity of sunlightã The UV Index rates the total intensity of UV light for many locations in the US daily: ... http://www.cse.clrc.ac.uk/msi/projects/ropa.shtml 7 12Two Ways to Think about Radiation Energy2. Total EnergyãThis relates not only to how much energy is in each packet but also to the total number of packets arriving at a ... deeper into the skin, leading to long term damageSource: N.A. Shaath. The Chemistry of Sunscreens. In: Lowe NJ, Shaath NA, Pathak MA, editors. Sunscreens, development, evaluation, and regulatory...