Is thermal radiation the same as infrared radiation?

Abstract

This article deals with the often simplistically understood question of the relationship between thermal and infrared radiation in school physics. In standard teaching, thermal radiation is usually associated exclusively with the transfer of energy during heat exchange, while the term infrared radiation is defined in optics as a specific range of the electromagnetic spectrum. Based on Planck's law, the author shows that thermal radiation covers the entire spectrum of electromagnetic waves, from X-rays and gamma rays to microwaves, with infrared radiation representing only a part of it. Calculations and graphs are used to demonstrate that low-temperature bodies emit mainly in the infrared range, while at high temperatures, visible and ultraviolet radiation also play a significant role. The article also points out that infrared radiation can also be generated by non-thermal processes (e.g., in semiconductor diodes or lasers). In conclusion, it is emphasized that infrared radiation cannot be equated with thermal radiation; it is only a part of it, and in physical terminology, a more accurate term would be "infrared thermal radiation."