Wien's Law

#physics#thermodynamics

Note

Relationship between temperature and emission of radiation. ∴ Any object that is above 0 K will be emitting some radiation

• Cool objects, such as the human body, emit radiation at long wavelengths with lower energy, such as infrared radiation. Infrared radiation is not visible by the naked human eye under normal circumstances.
• At higher temperatures, objects emit radiation with a higher frequency and you can see it glow red. An example is a bar heater that glows red hot.
• At even higher temperatures, say $2000K$, objects such as the filament of an incandescent light glow yellow or white.
• Very hot objects, at temperatures of $10^{6}K$ or more, emit the majority of their radiation within the gamma and X-ray regions of the electromagnetic spectrum.

Wien discovered that the peak wavelength at which an object will emit the maximum intensity of radiation is dependant on its surface temperature.

Wien's Law

${\lambda }_{max}\times T=2.898\times 10^{-3}mK$ where ${\lambda }_{max}$ is the peak wavelength of the emitted radiation in metres ($m$) and $T$ is the surface temperature of the object in kelvin ($K$).