Definitions for "Quantum Theory"
The theoretical basis of modern physics that explains matter and energy on a subatomic level. This includes the assumption that matter is made of discrete units or "quanta" of energy (Planck), that radiation is quantized in the same way (Einstein), that energy and matter are the same and can be a particle and a wave at the same time (de Broglie), that we cannot measure both the speed and location of a ceratin subatomic particle (Heisenberg) which most people know as "The Uncertainty Principle", and the Copenhagen Interpretation which states that a particle cannot have specific properties or even exist until it is measured (Bohr, Schrodinger). Most of us know this as the "observer effect", which shows that there exists no "objective" realtiy.
the study of the jumps from one energy level to another as it relates to the structure and behavior of atoms. (Basic Science/Magnetism/reviewatom/discussion004.htm)
Max Planck said the energy emitted in radiation (e.g., light) occurs in discrete quanta but acquires wavelike properties under certain conditions. Light is neither particles nor waves in the classical sense of the terms.