This is occurs when an atom either absorbs or emits energy when bombarded by a source.
Neils Bohr predicted that electrons moves round in the atom in distinct orbitals according to their energy. An electron in its ground state can become excited if it gains sufficient energy which surpasses that of its ground state configuration. An atom can also move from higher energy levels to lower ones. During the descent, energy is given off in form of emission spectra.
Absorption occurs when electrons in an atom absorbs energy from incoming radiation and they re-radiate it in all directions. This is given off as a spectra and can be observed for such electron.
Electrons absorb energy, as they absorb energy they go from ground state to excited state and to return to ground state electrons release energy in the form of photons producing that color.
