Quantum Mechanics: A branch of physics dealing with phenomena on a very small scale (like atoms), where wave-particle duality becomes significant.
Photon:A quantum particle carrying energy proportional to its frequency but having zero rest mass; essentially showing wave-particle duality by behaving both as particle and wave.
De Broglie Wavelength: The wavelength associated with a particle, demonstrating wave-particle duality by showing that particles can have wave-like properties.