Quantum Physic Flashcards
chapter 19 (13 cards)
Define photoelectric effect
Photoelectric effect is the emission of photoelectrons from a metal surface when electromagnetic radiation of a sufficiently high frequency is incident on it.
Define photon
A photon is a quantum of energy of electromagnetic radiation.
Define work function energy
Work function energy of a metal is the minimum amount of energy that will remove an electron from the metal surface.
Define threshold frequency
Threshold frequency is the minimum frequency of an incident photon that will remove an electron from the metal surface.
Einstein’s equation for photoelectric effect
E = Φ + KE_max
hf = hf0 + eVs (stopping potential)
hc / λ = hc/ λ0 + 1/2mv² (max velocity)
E = energy of incident photon
Φ = work function
KeE_max = max ke of ejected photoelectron
Define stopping potential
Stopping potential is the minimum potential difference between metal and collector that will prevent the most energetic photoelectron from reaching the collector, resulting in zero photocurrent.
Intensity equation
I = P / A
I = E / tA
I = Nhf / tA
(N is no. of photon arrived)
Saturation current equation
i = (N/t) e
N/t is rate of photoelectrons emission from metal surface
Line spectra evidence
1) each line on the line spectrum corresponds to a single wavelength and frequency of light, which implies that the photo energy is discrete.
2) Since energy of the emitted photon corresponds to the difference in energy levels in the atom, this implies that the energy levels must be discrete.
Define energy level
An energy level is the quantised energy corresponding to an allowed state of the electron within the atom.
Define de Broglie wavelength
The de Broglie wavelength is the wavelength associated with a moving particle.
p = h / λ
Define Heisenberg Uncertainty Principle
Heisenberg Uncertainty Principle states that it is impossible to measure the exact position and momentum at the same time.
∆x∆p >= h
