Hmmm. Never really worked with Optics all that much, but I shall try to think about how to detect the ElectroMagnetic emissions of a light source a bit more as opposed to the optical emanations of a device.
The optical emanations of a light source ARE electromagnetic emissions.
The history of our understanding of the electromagnetic spectrum is full of very interesting discoveries.
Maxwell in the 1800s was able to use the known properties of electric and magnetic fields to derive the speed of propagation of electromagnetic waves. Remarkably, the speed matched the already known speed of light. It was this "coincidence" which suggested later experiments which established that light was indeed a form of electromagnetic wave.
What has been traditionally referred to as "short wave", the neighborhood of 40 meter wavelengths, turn out to be some of the longest waves that one deals with in the various uses of electromagnetic waves. Light waves have wavelengths around the diameter of an atom, say about 1 angstrom.
One angstrom is 1e-10 meters, which means one-tenth of one-billionth of a meter. Now that is really a "short wave".
The reason why light doesn't penetrate the walls of a house is related to its wavelength. The close match between the wavelength of the light and the size of the atoms making up the wall causes a greater amount of interaction of the light with the wall. This is seen in the form of absorption of the light and conversion to heat or the reflection of the light.
The transparency of a window is due to the fact that much visible light is able to penetrate the window with very little interaction with the atoms in the window. In a similar fashion, radio waves of much longer wavelengths are able to penetrate walls because of the fact that they interact very little with the atoms in the walls.