Wave-particle duality: This is the concept in quantum mechanics that every particle or quantic entity may be described as both a particle and a wave.
Quantum mechanics: This is a branch of physics dealing with physical phenomena at microscopic scales, where the action is on the order of the Planck constant.
Electromagnetic spectrum: This is the range of all types of electromagnetic radiation, including light, radio waves, gamma rays etc., each having different photon energies.