I took the picture in the depths of winter. I've been teaching about black-body emission this year. This is another good example. I say that the heater gives off infra-red. If you are close by you can really feel it. However, infra-red is not visible but the heater is clearly giving off a lot of red. This shows that electromagnetic waves are given off over a range of wavelengths. It is merely that the peak for intensity is in the invisible range. Just imagine how bright that would look to our eyes.
