To my mind radio waves are different than light because they are described by fields whose energy is not a function of frequency but just the amplitudes. That they always have to surround their source, and are not uniquely associated with individual particles. Light on the other hand is described by photons and the photon's energy are dependant on frequency. A photon does not surround the source of it's emission, and it is associated with individual particles. Between the two descriptions is something called the infrared divergance. Physicist get around this difficulty with state equations where they either let the photon have effective mass by letting the action constant be one for light or zero for radio waves. It is really hard to find understandable information on the infrared divergance problem. The infrared divergance came into existance when Einstein explained the photo electric effect with photons, thereby solving one problem while creating another problem.