photoelectric effect

[Mary Shih 3J]

If long wavelength light is not ejecting electrons from a metal surface will increasing the intensity of the light result in electrons being ejected? Justify your answer.
No, because in this experiment light is not acting like a wave. If light were acting like a wave then the intensity would be proportional to the size (amplitude) of the wave and the bigger the wave the greater its energy.

What does it mean when the light is not acting like a wave? Was this covered in the lecture? if so can someone send the timestamp?

[Jagveer 1I]

That is a great question. In the photoelectric experiment they observed that increasing the intensity of the light did not eject electrons and they concluded that light was not acting like a wave. Instead it was acting like it was made of individual photons, where the individual photon's energy must overcome the energy that existed between the electron and the atom that made up the surface. Hopefully this helps.

[Nayra Gharpetian 3F]

That is a great question. In the photoelectric experiment they observed that increasing the intensity of the light did not eject electrons and they concluded that light was not acting like a wave. Instead it was acting like it was made of individual photons, where the individual photon's energy must overcome the energy that existed between the electron and the atom that made up the surface. Hopefully this helps.

Yes exactly! Scientists figured out that if the light acted like it was comprised of individual photons with enough energy to break the bond between the electron and the surface, the electron would be ejected. Also, one photon is capable of ejecting one electron.

[Mary Shih 3J]

That is a great question. In the photoelectric experiment they observed that increasing the intensity of the light did not eject electrons and they concluded that light was not acting like a wave. Instead it was acting like it was made of individual photons, where the individual photon's energy must overcome the energy that existed between the electron and the atom that made up the surface. Hopefully this helps.

So the ineffective light is acting as photons instead of a wave? It sounds like photons, as long as it as sufficient energy, can eject an electron. So not all photons are created equal right? Some photons don't have enough energy to eject an electron (seen in this case with long wavelength)?

[Jagveer 1I]

Yes, the light is acting like it is made up of individual photons instead of acting like a wave and it acts this way for both ineffective and effective light. Also, not all photons are equal, the amount of energy that each individual photon has depends on the light source. The light sources with shorter wavelengths tend to result in electrons being ejected even when the intensity of the light is low, so these photons had enough energy to overcome the threshold energy. On the other hand, light sources that had longer wavelengths and high intensity resulted in electrons not being ejected, so the photons did not have enough energy to overcome the threshold energy.

[Nicoli Peiris 1B]

If light were acting as a wave in this instance, increasing the amplitude which causes a bigger wave and a larger amount of energy would cause the electron to be ejected. However, this was not the case. So, we can see light is not acting like a wave. Instead it acts like a particle (photons) as higher frequencies cause the electron to be ejected.