> imagine a light that can manage to penetrate a bathroom wall, and tell me you don’t think it’s maybe a bit too powerful for consumer use ;) Visible light has

> imagine a light that can manage to penetrate a bathroom wall, and tell me you don’t think it’s maybe a bit too powerful for consumer use ;) Visible light has a wavelength of a few hundred nanometers; wifi is around 10 centimeters. Material penetrability varies enormously between different wavelengths (and between materials). Harm to humans also various enormously, and in a way very different from penetrability (for example, some wavelengths of UVC are very harmful to human skin but can be almost completely blocked by a thin sheet of clear glass). Equating penetrability with either 'power' or harmfulness is not a useful intuition. (incidentally, an incandescent light bulb emits on a blackbody spectrum, so some very small proportion of the energy it uses will be emitted at e.g. radio wave frequencies, which will certainly penetrate the bathroom wall)