lämpösäteisyyttä

Lämpösäteily, or thermal radiation, is electromagnetic radiation originating from the thermal excitation of charged particles within matter. All matter with a temperature above absolute zero emits thermal radiation. The hotter an object, the more intensely it radiates. This radiation spans a spectrum of wavelengths, with the peak wavelength inversely proportional to the temperature. For everyday objects, the peak emission is in the infrared part of the spectrum, making it invisible to the human eye but detectable as heat. Hotter objects, like the filament of an incandescent light bulb, emit radiation at visible wavelengths as well.

The process of thermal radiation does not require a medium and can travel through a vacuum, which is how the Sun's energy reaches Earth. The intensity and spectral distribution of the emitted radiation depend on the object's temperature and its emissive properties, known as emissivity. A perfect emitter, called a blackbody, emits the maximum possible radiation at a given temperature. Real objects have emissivities less than one. Understanding thermal radiation is crucial in fields such as thermodynamics, astronomy, and thermal imaging, where it is used to detect and measure temperatures of distant or inaccessible objects.