In the last 2 years I have heard at least 3 presentations given by "experts" on various topics of photoprotection and sunscreens. The speakers were faithful to the traditional classification of sunscreens as "chemical" and "physical," referring to the solubility or insolubility of the particles. Yet these labels seem to promote a misperception regarding how and why sunscreen agents protect the skin. The effectiveness of a sunscreen agent is based on its ability to absorb the selected wavelengths of light, whether in the visible (400- to 700-nm), UV-A (320- to 400-nm), or UV-B (280- to 320-nm) range.
Kollias N. The Absorption Properties of "Physical" Sunscreens. Arch Dermatol. 1999;135(2):209-a-210. doi:10-1001/pubs.Arch Dermatol.-ISSN-0003-987x-135-2-dlt0299