Threshold frequency & work function 2.4.2 Flashcards
what is the photoelectric effect
the phenomenon in which electrons are emitted from the surface of a metal upon the absorption of electromagnetic radiation
How does the photoelectric effect provide important evidence that light behaves as a particle
- light in quantised or carried in discrete packets
-each electron can absorb only one single photon
what is threshold frequency
the lowest frequency of radiation that can cause the photoelectric effect
–> the minimum frequency of light that can cause electrons to be emitted from a material
what is kinetic energy max
the theoretical max kinetic energy of a photoelectron once its left the material
what happens to the surface electron in photoelectric effect
the surface electron is emitted as the photon is absorbed by the surface electron overcome by the work function of the material
why does ultraviolet light work in the photoelectric effect
-ultraviolet light is a high energy light meaning that the photons will have enough energy
-the photons will have a very high frequency which overcomes the work function
why doesn’t red light work in the photoelectric effect
-red light is a low energy light meaning that photons will not have enough energy
-the photons dont have a high frequency meaning that the electrons dont have enough energy to overcome the work function
what is work function
the minimum energy needed to remove an electron from a metals surface
what is stopping potential
The potential difference required to stop photoelectron emission from occurring
what does the maximum kinetic energy of the photons depend on
- the frequency (or wavelength) of the incident photons
- the work function of the metal
Explain why there is a current only if the frequency of the electromagnetic radiation is above a certain value
-For there to be a current, electrons must be emitted from the surface of the photo emissive surface.
-Therefore when the electron absorbs a photon with energy higher than the work function of the material the energy of the photon is determined by its frequency
State and explain the effect on the current when the intensity of the electromagnetic radiation is increased
- more photons are indent on the surface
-therefore, more electrons absorb photons becoming a photoelectron
-therefore a higher current
what is the effect on stopping potential when the frequency of electromagnetic radiation is increased
-if frequency of a photon increases, energy of a photon would increase meaning that kinetic energy of the photoelectron emitted would be higher
-therefore a higher stopping potential would be needed to overcome the higher kinetic energy
