Frank L. H. Wolfs
Department of Physics and Astronomy, University of Rochester, Slide 16
Einstein's Theories:
The photoelectric effect.
¥Einstein explained this effect by interpreting light as a collection of photons with a discreet energy.
¥Einstein proposed that the photon energy is only determined by the wavelength of the light.
¥Changes in light intensity reflect changes in the number of photons, not the energy of the individual photon.
¥The resulting wave-particle duality also predicted that "particles" can behave like waves.  It was observed that for example electrons can behave like waves (electron diffraction).
http://www.faqs.org/docs/qp/chap03.html
http://www.matter.org.uk/diffraction/electron/electron_diffraction.htm