Answer:
Quantum theory.
Step-by-step explanation:
Neil Bohr's in the 1913 delivered a theory which is for the hydrogen atom which is based on the theory of quantum which says energy is transferred only in certain quantities which is well defined.
Electrons which are moving in outer orbit should moves around or about the nucleus.
When going from one level to another level energy is emitted or absorbed which is based on when electron jump from higher level to lower level emission of light quantum is takes place.