You'll find elements of the electromagnetic spectrum that the human eye can’t see. This includes thermal infrared radiation. This is often radiation with extended wavelengths. Almost everything emits thermal radiation - even individuals. Objects like a stove aspect on substantial, emit radiation from the visible spectrum when it glows ‘red’ https://handheldthermalimagers25602.blogsidea.com/36676301/facts-about-handheld-thermal-imagers-revealed