1. The Photoelectric effect Flashcards
What is the Photoelectric effect?
The photoelectric effect is an effect where if you shine radiation of high enough frequency onto the surface of a metal, it will instantly emit electrons.
Why does the photoelectric effect occur?
The photoelectric effect because most metals have ‘free electrons’ (electrons not bound to any atom) these electrons on or near the surface of the metal absorb energy from the radiation making them vibrate. If they absorb more energy than the work function of the metal, they can break free from the metal and become photo electrons.
What is the first conclusion drawn from the photoelectric effect?
For a given metal, no photoelectrons are emitted if the radiation has a frequency below the threshold frequency
What is the second conclusion drawn from the photoelectric effect?
The photoelectrons are mitted with a variety of kinetic energy ranging from zero to some maximum value. This value of maximum kinetic energy increases with the frequency of the radiation
What is the third conclusion drawn from the photoelectric effect?
The intensity of radiation is the amount of energy per second hitting an area of the metal. The maximum kinetic energy of the photoelectrons is unaffected by varying the intensity of the radiation.
What is the fourth conclusion drawn from the photoelectric effect?
The number of photoelectrons emitted per second is proportional to the intensity of the radiation.
What caused the Electromagnetic radiation to be theorised to not be a wave?
The threshold frequency and the kinetic energy of photoelectrons are what caused Electromagnetic radiation to be theorised as not being a light
How did the threshold frequency make it so that Electromagnetic radiation was not theorised to act as a wave
If electromagnetic radiation acted as a wave, all electrons would get energy slowly and gradually become photoelectrons, no matter the frequency. however this does not happen, as the frequency needs to be greater than the threshold frequency, so the wave theory can’t explain the threshold frequency
How did the kinetic energy of Photoelectrons make it so that electromagnetic radiation was not theorised to act as a wave?
The higher the intensity of the wave, the more energy it would transfer to each electron, however the kinetic energy of the photoelectrons only depends on the frequency of the Electromagnetic Radiation, so the wave theory does not explain the kinetic energy of photoelectrons?
So what model of the Electromagnetic radiation does explain the Photoelectric effect
The Photon model of light
What is the Photon Model of light
The photon model of light is used to explain EM waves, it is said that the energy they carry can only exist in discrete packets, with these packets being called photons.
How does the Photon Model of light explain the Photoelectric effect?
Each photon has a one-on-one, particle-like interaction with an electron in a metal surface. Each photon would transfer all its energy to one specific electron. meaning that instead of the intensity of the electromagnetic radiation affecting the Photoelectric effect, its the frequency of the photons arriving that affects it.
What is the work function?
The work function is the minimum amount of energy needed to break the bonds holding an electron to a metal.
What is stopping potential?
Stopping potential is the potential difference needed to stop the fastest moving electrons travelling with a maximum kinetic energy, it can be used to measure the max kinetic energy
