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Post by
Whampoa on May 12, 2024 11:51am
Breaking News from a couple of weeks ago: MIT News
This MIT & Tokyo have been researching how evaporation works for years. They ruled out temperature differential, then hypot it was pressure, now its sunlight (for us its electromagnetic waves). Prior they were looking to understand evaporation for industrial optimization. That is still the same objective but now included calculation of climate.
How light can vaporize water without the need for heat
Surprising “photomolecular effect” discovered by MIT researchers could affect calculations of climate change and may lead to improved desalination and drying processes.
David L. Chandler | MIT News
Publication Date:
https://news.mit.edu/2024/how-light-can-vaporize-water-without-heat-0423 In a series of painstakingly precise experiments, a team of researchers at MIT has demonstrated that heat isn’t alone in causing water to evaporate. Light, striking the water’s surface where air and water meet, can break water molecules away and float them into the air, causing evaporation in the absence of any source of heat.
It could also lead to new ways of designing industrial processes such as solar-powered desalination or drying of materials. One key indicator, which showed up consistently in four different kinds of experiments under different conditions, was that as the water began to evaporate from a test container under visible light, the air temperature measured above the water’s surface cooled down and then leveled off, showing that thermal energy was not the driving force behind the effect.
Other key indicators that showed up included the way the evaporation effect varied depending on the angle of the light, the exact color of the light, and its polarization. None of these varying characteristics should happen because at these wavelengths, water hardly absorbs light at all — and yet the researchers observed them.
The effect is strongest when light hits the water surface at an angle of 45 degrees. It is also strongest with a certain type of polarization, called transverse magnetic polarization. And it peaks in green light — which, oddly, is the color for which water is most transparent and thus interacts the least.
way more..
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