If you place an object in the sun, it will heat up because it absorbs energy from the sun’s rays and converts it into heat. However, there is a limit to how much warmer the object can get. Even a person sunbathing on a beach won’t catch fire.
When objects or people absorb energy (light) from the sun, they also emit energy in the form of heat (infrared radiation). You may have experienced this when walking past a block wall on a summer afternoon and feeling the heat coming from it.
Kirchhoff’s law of thermal radiation, developed by Gustav Kirchhoff in 1860, explains the relationship between an object’s ability to absorb and emit energy in the form of electromagnetic radiation. According to this law, the absorptive and emissive efficiencies are equal at each wavelength and angle of incidence.
A new device created in the lab of Harry Atwater, the Howard Hughes Professor of Applied Physics and Materials Science, challenges the traditional relationship between absorbed and emitted efficiencies of an object. This invention could have significant implications for sustainable energy harvesting systems and the development of certain types of camouflage.
The research paper titled “Direct Observation of Kirchhoff Thermal Radiation Law Violation” is published in the July 24 issue of the journal Nature Photonics.
2023-07-26 08:00:03
Source from phys.org