The wavelength of the wave associated with a moving particle. The wavelength (λ‎) is given by λ=h/mv‎, where h is the Planck constant, m is the mass of the particle, and v its velocity. The de Broglie wave was first suggested by Louis de Broglie in 1923 on the grounds that, since electromagnetic waves can be treated as particles (photons), one could therefore expect particles to behave in some circumstances like waves (see complementarity). The subsequent observation of electron diffraction substantiated this argument and the de Broglie wave became the basis of wave mechanics.