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Light deforms water

Tecnociencia water1adaniel buenoLight particles, called photons, exert pressure on the objects they reach. Until recently, physicists debated which formula should be used in calculations of the force of light on transparent materials, that proposed by Hermann Minkowski in 1908, or that formulated by Max Abraham in 1909. Theoretical studies in the 2000s confirmed that, actually, both formulas are valid. No laboratory experiment had precisely confirmed this conclusion until a team led by Nelson Astrath, of the State University of Maringá (UEM) and Utah State University, analyzed the waves of just a few millionths of a millimeter that were created by the force due to the light of a laser beam focused on a small water surface (Nature Communications, July 2014). “The pressure exerted by the laser we used on the water was about 300,000 times smaller than atmospheric pressure at sea level,” explained one of the study’s authors, Luis Carlos Malacarne of UEM. “The deformation that we measured in the water can be calculated using equations based on both interpretations of the force of light.”