Louis de Broglie
Approach: unify ideas of Planck and Einstein (light is quantized) with those of Bohr for the atom.
- We know light is a wave (inteference effects) which sometimes acts like a particle (Planck’s quanta, Einstein and the photoelectric effect).
- If light (manifestly a wave) can sometimes be also viewed as a particle, why cannot electrons (manifestly a particle) be sometimes viewed as a wave?
Additional motivation: Quantization rules occur naturally in waves. Perhaps Bohr’s quantization rule might be understood in terms of “matter waves”.