VALENCIA, Spain, July 21 (UPI) -- Thirty-four percent of ultraviolet radiation gets underneath canvas beach umbrellas, researchers in Spain say.
Researchers from the University of Valencia in Spain explain canvas has a very high capacity for absorbing radiation and intercepts most full direct sun rays. However, they say, the umbrella does not protect from the diffused radiation that penetrates through from the sides.
The study, published in the journal Photochemistry and Photobiology, finds part of the diffused radiation that makes up approximately 60 percent of the total reached a sensor positioned under the umbrella.
"We have proven that irradiance -- radiation incidence per unit of surface area -- that reaches the ground covered by an umbrella is 34 percent of the total," study co-author Jose Antonio Martinez-Lozano says in a statement.
Martinez-Lozano and colleagues positioned an ultraviolet ray sensor on the base of a canvas beach umbrella painted blue and white and also developed a geometric model.
The model calculated the irradiance received on the different horizontal and vertical planes under the umbrella. In the case of horizontal irradiance, the values the model provides coincide with those registered experimentally with a relative error of 3 percent.