Quantum and Nuclear Physics (topic 7 & 12) Flashcards
The Photoelectric Effect
Refers to the emission of electrons from a metal surface as a result of the absorption of electromagnetic wave energy. Shows how light (usually thought of as a wave) can exhibit particle-like behavior.
Davisson-Germer Experiment
Electrons were scattered from atoms and these scattered electrons produced an interference pattern just like waves.
Thomas Young’s Double Slit Experiment
Shows wave behavior of light
Electron Diffraction
Shows how electrons (usually thought of as particles) can exhibit wavelike behavior (diffraction and interference).
Beta Decay
Is a process by which a nucleus emits an electron or positron. It does not showcase any wave-particle duality.
Bohr’s Model for the Hydrogen Atom
The angular momentum of the electron is quantized having values that are multiples of h/2π
Photon Energy Equation (E)
E = hf or λ = hc / E
where
E = photon energy (eV or J)
h = Planck’s constant
f = frequency (Hz)
c = speed of light
λ = wavelength (electromagnetic wave)
E is proportional to its frequency
Work Function Equation (phi)
φ = h f0
where
φ = Work function (phi)
h = Planck’s constant
f0 = threshold frequency (f0)
The De Broglie Hypothesis
Suggests that all matter exhibits wave-like properties. In particular, the momentum of a particle is related to its wavelength where the De Broglie wavelength may be deduced by the following formula:
p = h/λ -> λ = h/p -> λ = h/mv
where
p = momentum
h = Planck’s constant
λ = wavelength
m = mass
v = velocity.
Wave-Particle duality
refers to matter acting as both waves and particles.
Quantum
Refers to the smallest discrete amount of something.
Photon
Is a quantum of electromagnetic radiation (light). Exhibit wave properties under refraction or interference. Exhibit wave properties under its emission or absorption.
Angular Momentum Equation
mvr = nh / 2π
where
m = mass of electron,
v = speed of electron,
r = radius of orbit,
n = interger,
h = Planck’s constant.
Schrödinger model of the atom
P(r) = |φ|^2 multiplied by Δv
where
P(r) = probability of finding an electron in a small volume,
|φ|^2 = amplitude of wave function squared,
Δv = small volume.
Heisenberg’s Uncertainty Principle
The act of observing (making a measurement) alters the system.
Heisenberg’s Uncertainty Equation
Δx multiplied by Δp is greater than or equal to h / 4π
OR
ΔE multiplied by Δt is greater than or equal to h / 4π
where
Δx = uncertainty on position,
Δp = uncertainty on momentum,
ΔE = uncertainty on energy,
Δt = uncertainty on time,
h = Planck’s constant
Nuclear Radius Equation
R = R0 multiplied by A^1/3
where
R = nuclear radius (m),
R0 = Fermi radius constant,
A = atomic mass number
What happens when Alpha decay occurs
Add Helium 4
What happens when Beta decay occurs
Add a Beta minus (electron) + anti-electron neutrino
OR
a Beta plus (positron) + electron neutrino
Decay Equation
N = N0 multiplied by e ^ -λ t
where
N = final mass (or activity),
N0 = initial mass (or activity),
t = time elapsed,
λ = decay constant = probability of decay at a certain time.
Decays / Seconds unit
Becquerel
Half-life Equation
T1/2 = ln2/λ
where
T1/2 = half-life of exponential decay,
ln = natural log.
Element notation
Number on top of the molecule = mass # (number of nucleons) n + p
Number at the bottom of the molecule = atomic # (# of protons)
Isotopes
Same atomic number, different mass number
Energy levels
Electrons get excited, go up in energy level. When they go back down, they emit a photon (light) with energy
Energy is quantized - only comes in multiples of h
Energy levels (wavelengths and frequencies)
Smallest λ -> highest f and largest E
Two types of Beta decay
- Electron-beta decay
- Positron-beta decay
Gamma decay
γ = photon
**no charge
Exponential decay
As parent particles lessen, daughter particles increase
Binding energy
The energy released when a nucleus is assembled from its constituent parts. Every time a new element is made, there’s an energy that’s released.
Mass of left hand side ≠ mass of right hand side
Einstein’s famous equation
ΔE = Δm c^2
where
ΔE = binding energy (eV or J)
Δm = mass defect (kg or u or (MeV) / c^2)
c = speed of light = 3 x 10^8 m s^-1
6 types of quarks (every particle also has an anti-particle)
- Up
- Charm
- Top
- Down
- Strange
- Bottom
Hadron
Particle made of quarks
ex. Baryon, Meson
Baryon
Particle made of three quarks
Meson
Particle made of two quarks (one quark + one anti-quark)
Leptons
Other than quarks, there are other fundamental particles called leptons
6 types of leptons (every particle also has an anti-particle)
- τ- = tau
- µ- = mu
- e- = electron
- ντ = tau-neutrino
- νµ = mu-neutrino
- νe = electron-neutrino
Conservation
The idea that properties must be conserved (same before as after)
Higgs boson
Responsible (through interactions) for mass
4 main bosons
- g = gluon
- W+, W- = W-boson
- Z° = Z-boson
- γ = photon
Strength of fundamental forces
Gravitational < Weak nuclear < Electromagnetic < Strong nuclear
Band of stability in nuclei
- The darker the points, the more stable
- Nuclei further from the dark region are increasingly unstable and will quickly decay back into a more stable form
- Band of stability lies above the one to one ratio of protons and neutrons
- the stability of nuclei depends on the attractive and repulsive force
- the band of stability implies that the strong nuclear force must be very short-ranged in nature
