Planck Constant: The Planck constant is a fundamental physical constant that represents the smallest possible change in the energy of a system, and is a key parameter in the theory of energy quantization.
Photon:A photon is a discrete packet of electromagnetic radiation, which is the fundamental unit of light and other forms of radiant energy.
Blackbody Radiation:Blackbody radiation is the thermal radiation emitted by an idealized perfect absorber and emitter of radiation, which provided the experimental evidence that led to the development of the concept of energy quantization.