Quantum mechanics (QM) is briefly defined as a body of scientific principles describing the behavior of matter and its interactions on both the atomic and subatomic scales.
QM’s development, a revolution in physical theory, is the result of physicist coming to terms with the limitations of classical physics. The principles of QM are difficult for the human mind to comprehend.
This is mainly in part by the fact that humans are accustomed to reasoning in regards to the world on a scale where classical physics is an exceptional approximation. QM is counterintuitive, and in the words of Richard P. Feynman, a founder of quantum electrodynamics (QED), “I hope you can accept Nature as She is – absurd.”
Many fundamental components of the universe exhibit wave-particle duality where their behavior is in some ways particle-like and in other ways wave-like, such as photons (discrete packages of light). In regard to electromagnetic radiation, the laws of QM predict such energies, colors, and spectral intensities.