 These experimental results provided confirmation of Albert Einstein 's photoelectric effect and Planck 's relation ( E = fh ) linking energy ( E ) and frequency ( f ) arising from <unk> of energy with Planck 's constant ( h ) . But they also provided evidence supporting the model of the atom that had been proposed the previous year by Niels Bohr . Its key feature was that an electron inside an atom occupies one of the atom 's " quantum energy levels " . Before a collision , an electron inside the mercury atom occupies its lowest available energy level . After the collision , the electron inside occupies a higher energy level with 4 @.@ 9 electron volts ( eV ) more energy . This means that the electron is more loosely bound to the mercury atom . There were no intermediate levels or possibilities . 
