3.2 More About Photoelectricity + Graph And Explination Flashcards
What did max plank suggest
The energy of each vibrating atom is quantised (only certain levels of energy are allowed)
Energy could only be in multiples of a basic amount, or quantum, hf where f is the frequency of vibration and h is Plancks constant .
What did both Einsteins photon model and planks theory of vibrating atoms show about energy
Shows that energy is quantised
Conduction electrons
Move about a random in a metal like molecules of gas
Average kinetic energy of a conduction electron depends on the temperature of the metal
What value is the work function of a metal
10^-19
What happens if a metal does not have enough energy to exceed the work function
It does not leave the metal but it collides repeatedly with other electrons and positive ions and quickly loses its extra kinetic energy
What is a vacuum photocell
A glass tube that contains a metal plate (photocathode) And a small metal electrode (anode)
What happens in a photocell when light with a frequency greater than the threshold frequency is shone at it
Electrons are emitted from the cathode and are attracted to the anode
The micro ammeter in a circuit can be used to measure the photo electric current

What is the photo electric current
The number of electrons per second that transfer from the cathode to the anode
The number for photoelectrons per second that transfer from the cathode is equal to
Current (I) / e
Where e is the charge of the electron
What is the photo electric current proportional to
The intensity of the light incident on the cathode
What is light intensity
A measure of of the energy per second carried by the incident light
which is proportional to the number of photons per second incident on the cathode
Why are the number of photons emitted per second proportional to the intensity of light
Because each photoelectron must have absorbed one photon in order to escape from the metal surface
What does the intensity of incident light not effect
The maximum kinetic energy of the photon electron.
This is because the energy gained by a photoelectron is due to the absorption of one photon only
Ekmax=hf-work function
What can the maximum kinetic energy of the photoelectron emitted for a given frequency of light be measured using
A photocell
