Thermal radiation is produced by a microwave oven to heat food. Thermal radiation includes microwave radiation. For some reason, pre-college instructors and textbooks erroneously believe that heat radiation and infrared radiation are the same thing. The electromagnetic spectrum includes radio waves, microwaves, infrared waves, visible light, ultraviolet light, X-rays, and gamma rays, all of which carry energy. All frequencies of radiation can constitute thermal radiation since they all cause an item they encounter to get heated. The term "thermal radiation" is used by physicists to describe radiation that may heat up an item when it comes in contact with it. Or they refer to a wide range of frequencies with a specific form that changes depending on the temperature of the emitter.
2000 K thermal spectrum
This graph displays the frequency spectrum of the thermal radiation that a 2000 K-temperature blackbody object emits. Even while the infrared range of frequencies accounts for the majority of thermal radiation, some thermal radiation also manifests as microwaves, visible light, and ultraviolet radiation. To make the curve simpler to interpret, take note that both the frequency axis and the power axis are represented on logarithmic scales. Image in the public domain, by Christopher S. Baird.
The peak in the spectrum of a glowing substance's radiated radiation rises to higher frequencies the hotter the body is. Thus, astronomers may calculate a star's temperature by observing the relative brightness of various frequencies in its light. In this context, the term "thermal" refers to the relationship between the temperature of the radiation source and its spectral form. "Non-thermal radiation" on the other hand refers to light that is unrelated to the source's temperature. For instance, unlike a heated filament, lasers use a different process to generate light. As a result, the laser light is not thermal radiation and is independent of the laser's temperature. However, laser light continues to carry energy and has the power to heat up nearby things. If, as many pre-college teachers do, you define "thermal radiation" as radiation that conveys energy and heats objects, then all radiation, regardless of frequency or spectral structure, falls under this definition. Through electromagnetic radiation, a microwave oven heats soup in exactly the same manner as a campfire heats campers. Perhaps because live human bodies are at a temperature where their thermal radiation peaks in the infrared, there is a misconception that only infrared radiation is thermal. A soldier wears infrared goggles to spot human beings at night. The thermal radiation from the sun, however, peaks in the visible light frequency range and is just as hot. In actuality, the atmosphere absorbs the majority of the infrared spectrum of sunlight, preventing it from reaching humans on the surface. Despite having very little infrared radiation, sunlight has little trouble heating us up, and its spectral structure is related to the sun's warmth.
