finish these three questions

1) How would you explain the wave-particle dualism? Provide your explanation by referring to the Young’s experiment (two-slits experiment) and the De Broglie equation.

2) Explain the photoelectric effect, by referring to the experiment set up and the physics behind it. In particular, explain the concepts of work function, activation frequency and photon flux.

3) According to the Kronig-Penney model used to derive the band theory of solids (non metals), how would you explain the presence of energy bands in a material, such as a semiconductor? Sketch an example of a 4 bands E vs k diagram within the Brillouin zone. One of the interesting concepts related to the E vs k diagram is the effective mass concept. Explain this concept and how it is related to the diagram