In an Einstein like gedanken experiment, the relativistic changes of energies of a photon and a rest mass particle caused by the same relative movement were compared and it was found, that the same relative movement was causing very different energetic changes on the photons and rest mass particles: photons have significantly more “capacity” for kinetic energy. To explain this phenomena, which could be named kinetic capacity effect, a physical model of a “folded and looped photon” was created and checked quantitatively through relativistic Doppler effect for kinetic and total energies, and for linear momentum. De Broglie’s material wave was identified as modulation wave of two interfering waves of the correlated half photons inside of the particle, resulting in known group and phase velocities. Photons themselves were not changed in physical description, so Quantum Mechanics will stay in use with them, and Special Relativity has now extended abilities for entering into particles, opening a way through discussed model to unify both theoretical worlds. For the moment, the two classical theories, waves and relativity, have confirmed exact the hypothesis of present model.