4.5 - Quantum Physics Flashcards
What are photons ?
They are particles of light
How is the energy of a photon related to the wavelength of the light ?
E = hf
with Energy being inversely proportional
What is “h” in E = hf
h is Planck constant (6.63x10^-34) ,measured in Js
What can be measured in electron volts (eV)
Energy
What is the photoelectric effect ?
When shining light with enough energy onto a metal releases electrons (and can cause a current to flow)
What shows that light could be a particle ?
If light was a wave increasing the intensity of the light would also increase the energy of the electrons released, but they are not. Instead energy of the electron depends on the frequency of the light
How many photons does each photoelectron absorb prior to emission ?
Only 1
How does photon model of light explain threshold frequency seen in the photoelectric effect ?
Each electron absorbs a single photon. This photon must have enough energy for the electron to be released if it doesn’t the energy is re-emitted. The electron can’t build up energy as it could if light was a wave.
What is threshold frequency ?
The threshold frequency is the lowest frequency below which the photoelectric effect does not occur
What is work function ? (ϕ)
Minimum amount of energy an electron required to leave the surface of a metal (ϕ)
What is the equation relating the energy of an incident photon to the work function and the kinetic energy of released electrons.
Photon Energy = work function + kinetic energy
What is another way to write work function ?
ϕ = hc/λ
What is the photon energy equation ?
E = hf
e = h x c/λ
λ = hc/E
What is de Broglie’s equation ?
λ = h / p
wavelength = Planck’s constant x momentum
momentum = mass x velocity
