Bohr in his structure of atom explained that electrons revolve around the nucleus in fixed orbit or shell or energy levels.These energy levels are stable and are stationary along with different energy value.
A electron can jump to higher energy levels on absorbing the enough energy required to do so.
The electron in higher energy level is unstable and thus gets back to its original state by emitting the energy absorbed.
Thus electron would jump to a higher energy level when it absorbs enough energy.
