There are only two fundamental physical modes of energy transfer, conduction and radiation. In conduction, energy slowly diffuses through a medium from a point of higher temperature to a point of lower temperature, whereas in radiation, energy is transmitted with the speed of light by electromagnetic waves (or photons), and a transmitting medium is not required. Thus from a conceptual viewpoint, convection is not a basic mode of heat transfer. Instead, it occurs by a combined effect of conduction (and/or radiation) and the motion of the transmitting medium.