# Photoelectric effect

1) Why the existence of a threshold frequency for the photoelectric (external) effect is in favor of the photon (corpuscular) theory and not of wave like theory?

2) Explain why, even in the case of illumination with monochromatic light, there is a distribution over speeds of the emitted electrons. Why in the case of monochromatic radiation thin metallic films ($10^{-7} -10^{-8} cm$) emit electrons having more homogeneous (more equal) speeds.

3) Why photoelectric measurements are so sensitive to the nature of the surface of the material used in photoelectric effect?

4) The theory of photoelectric effect of Einstein where light is considered having corpuscular nature, is against the Young double slit interference experiment?

1) If the interaction is produced between an electron and a photon, the electron needs to receive from the photon an energy at least equal to the extraction energy (work function). If the interaction would be between an electron and an electromagnetic wave, the electron should leave the metal atoms for any value of the wave intensity (it is obvious that the time needed to emit the electron would be different). This is not happening in reality and the experimental results are different.

2) The electrons emitted by a metal have not all the same speed, given by the Einstein theory. The majority of the electrons have smaller speeds. This is due to the fact that light interacts with electrons of the substance both at the surface and at a certain depth in the material. If an electron is extracted from the interior of the substance, it loses a part of its initial energy to reach the surface. For the same reason also thin films give extracted electrons with more homogeneous speeds.

3) In this case the nature and the condition of the material surface influence the value of the work function of the material.

4) No, the corpuscular theory is not against the Young double slit experiment. Light is having a dual nature and both aspects of light (corpuscular and wave like) are simultaneous valid.

Until now, there is no experiment to show simultaneous both aspects; some experiments shows the wave like behavior of light and other experiments shows the corpuscular aspect of light.