MIT Challenges Conventional Understanding of Evaporation

We commonly understand that water evaporates with rising temperatures, but researchers have unveiled another critical element. This revelation could unravel enduring atmospheric puzzles and pave the way for future technological strides.

The breakthrough by the MIT team reveals that visible light can dislodge water molecules at the air-water interface, causing them to escape into the air. In essence, while temperature fluctuations have historically driven evaporation, light beams alone can also prompt water to transition into vapor.

The researchers have named this phenomenon the “photomolecular effect,” drawing parallels with the photoelectric effect described by Einstein in 1905, where light particles can release electrons from atoms upon impact.

Xiulin Ruan, a professor of mechanical engineering at Purdue University who wasn’t part of the MIT study, commented on this discovery published in the journal PNAS, stating, “The revelation that light, rather than heat, can drive evaporation offers groundbreaking insights into light-water interactions.”

He further elaborated, This could enhance our comprehension of how sunlight interacts with natural water sources like clouds, fog, and oceans, influencing weather and climate.

Additionally, it holds promising practical applications, such as solar-powered high-efficiency water desalination. While such revolutionary findings may face initial skepticism, they often take time to be embraced by the scientific community.

Unraveling an Enigma

While the difference between light-induced and heat-induced evaporation might appear subtle, researchers believe it could significantly influence future evaporation-based projects.

Moreover, it might help resolve longstanding discrepancies related to cloud formations.

Solving an age-old puzzle, measurements of how clouds absorb sunlight have consistently shown they absorb more than physics traditionally allows. The photomolecular effect, inducing unexpected evaporation, might offer the missing piece to this mystery.

Double-checking

The MIT researchers were so intrigued by the discovery of light-induced evaporation that they conducted 14 additional experiments to confirm their findings.

Using laser light, they discovered that the most significant evaporation occurred when the light, polarized in a specific manner known as transverse magnetic polarization, hit the water surface at a 45° angle.

Surprisingly, the strongest effect was observed with green light, despite it being the color that least interacts with water, making it appear transparent.

Shannon Yee, an associate professor of mechanical engineering at Georgia Tech not involved in the study, commented on the findings: “The observations in the study introduce a new physical mechanism that fundamentally changes our understanding of evaporation kinetics.

It’s surprising that we are still uncovering new aspects of something as common as water evaporating.

Companies have shown interest in leveraging the photomolecular effect for various applications, such as drying paper in mills and evaporating syrup. However, the researchers believe that further exploration could greatly expand the potential uses of this phenomenon.

“This discovery has broad implications, but our initial experiments are just scratching the surface,” notes Gang Chen, MIT professor of power engineering and co-author of the study.

“Fully understanding and quantifying this effect requires extensive experimentation. We need to delve deeper into the properties of water and explore its application to other substances, including liquids and solids.”

Read the original article on: New Atlas

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