Determination of Work Function, Photoelectric Effect Flashcards
What is the main piece of evidence that light acts as a particle?
The photoelectric effect
What does the energy of one photon equal?
hf
What do we find if we shine light at a metal surface?
We see electrons being popped off
If the wave model of light was correct, what would the frequencies of the liberated electrons be?
Electrons liberated should have any frequency of light. However this is not the case
Why are liberated electrons able to move away from the metal?
They have kinetic energy
How do we use an evacuated tube to calculate the kinetic energy of the electrons?
- Shine light on plate
- Electrons are liberated
- Current is set up in circuit
- Set voltage to oppose current flow
- Turn up voltage until no electrons reach other side=stopping potential
- V=E/Q
What is the threshold frequency?
The minimum frequency required for electrons to be liberated
What is the relationship between the frequency of light and the kinetic energy of the electrons?
The higher the frequency, the more kinetic energy the electrons are liberated with
Why do we have to reach a certain threshold frequency before we start to see electrons being liberated?
A certain amount of energy is required for electrons to be liberated
What is the work function?
The amount of energy required to remove an electron from the metal surface
How do you find the work function from a kinetic energy - frequency graph?
Extrapolate the graph back to the y-intercept to find the work function
What does EK max equal?
EK max = hf - work function
When one photon strikes the surface of a metal, what happens?
It transfers energy hf to an individual electron. Some of this energy goes to releasing the electron, and any remaining energy is transferred as kinetic energy of the electron
What equation relates planck’s constant, the work function and the threshold frequency?
threshold frequency = work function / h
What did using a higher intensity of light striking a metal surface not increase?
The kinetic energy of the photons liberated, meaning that one photon is absorbed by 1 electron. 2 photons cannot be absorbed by the same electron, meaning that light exists as quanta, not just as one wave
