Full Idea
How could it be that the same radiation that produces interference patterns, and therefore must consist of waves, also produces the photoelectric effect, and therefore must consist of moving particles.
Gist of Idea
Radiation interference needs waves, but radiation photoelectric effects needs particles
Source
Werner Heisenberg (Physics and Philosophy [1958], 02)
Book Reference
Heisenberg,Werner: 'Physics and Philosophy' [Penguin 1989], p.23