The proof of the existence of the constant rest mass for photons in several ways
The photoelectric effect proves that the light must be consisting of particles and on the other hand the wave nature of light was shown through the double-slit experiment of Thomas Young. In this experiment, we could observe the interference fringes that justify the light as a wave. But we know that the constant mass of the electron was proven and electron, the same as photon, have interference fringes in the double-slit experiment. Therefore, there is at least one example that a particle with constant rest mass has interference fringes in the double-slit experiment and the removal of constant rest mass, for photon, is not a good solution to answer the observance of interference fringes in the double-slit experiment. In this paper, we explain different real examples in different branches of physics to demonstrate violations in the Conservation of mass and energy principle, such as: The relationship between temperature of a cavity and the wavelength of the emitted spectrum of a solid-state laser, the dependence of the performance of solar cells and the wavelengths of light, etc. It seems that we need to use a new theory about photon to improve all branches of physics which encounter with photon.