Ampere-Maxwell equation can predict the speed of light by assuming light as a traveling wave. However, it can not predict such characteristics as light generation, moving in a specific direction as a particle and dependence of wavelength upon its energy. Therefore, it needs to be noted that Ampere-Maxwell equation is very limited in predicting characteristics of light. While physics law should be applied to all the inertial frames, co-variance that mathematical form of the equation describing the physics law is same in all the inertial frames is not essential requirement to be physics law. Therefore, Lorentz transformation to result in both the co-variance of Ampere-Maxwell equation for light and the constant velocity of light in all the inertial frames is not the essential requirement. Considering light as a discrete particle with wave characteristics inside, analysis of double slit experiment indicates that travel direction of each photon after slit would be decided at the slit by interaction of incident photon with the slit including its materials and geometry to result in the interference pattern at the screen. There is no direct evidence of occurrence of superposition of photon in the slit and interference of the photon at the screen to result in the interference pattern. If there is no superposition of photon, quantum mechanics and entanglement of photon related with photon superposition need to be updated.