Electromagnetic Spectrum

The amount of energy a photon has makes it sometimes behave more like a wave and sometimes more like a particle. This is called the "wave-particle duality" of light. It is important to understand that we are not talking about a difference in what radiation IS, but only in how it behaves. Low energy photons (such as radio) behave more like waves, while higher energy photons (such as X-rays) behave more like particles.