The discussion explores the derivation of the de Broglie wavelength (y=h/p) from the equations E=hf and E=mc^2 within the framework of Special Relativity. It establishes the relationship between energy, momentum, and periodicity in different reference frames, highlighting the equation E2(p) = m2 c4 + p2 c2. The derivation leads to the relativistic dispersion relation, linking time periodicity and spatial periodicity. The analysis concludes with energy quantization that aligns with conventional quantum field theory, confirming the consistency of the approach with established principles. This synthesis of concepts underscores the interconnectedness of relativity and quantum mechanics.