de Broglie's eqn. proof goes this way:--- E = m*c2 E = h*c/L (L - Wavelength) the they are equated - m*c2=h*c/L => L=h/(m*c) But in E=m*c^2, m is the mass lost by some body to give energy E not mass of photon, then why do we consider m mass of photon ?? By considering that we find equivalent eqn.-- L=h/(m*v) for any mass m. Isn't that wrong??