I know It is not EM wave. It is not probablity wave since probablity can never be negative. But I think De Broglie's wave length for particles (like electron) is derived using equation of mass-energy equivalence. It infers that this wave carries energy ;for this wave-length is same as that of EM energy equivalent to the particle (E=mc^2). Certainly the particle is not spontaneously changing to EM wave then again this EM wave somehow give rise to a particle. So why have we used this equation to find the wave nature of particle? What is it's significance? #Electron is both particle and wave. What kind of wave? It is a naive question from a novice and ignorant person, interested in quantum physics. please respond.