What was the main idea of Thomson’s plum pudding model?
The atom was a diffuse positively charged sphere with electrons embedded throughout.
What experiment tested the plum pudding model?
Rutherford’s alpha particle scattering experiment using gold foil.
What unexpected observation did Rutherford’s experiment find?
Some alpha particles scattered at very large angles, including backwards.
The diffuse positive charge could only produce small deflections, not large ones.
What conclusion did Rutherford draw from his scattering experiment?
The atom contains a small, dense, positively charged nucleus with most of the mass.
Why is Rutherford scattering considered the birth of nuclear physics?
It established the existence of the atomic nucleus.
What assumptions are used in Rutherford cross section?
Coulomb interaction between alpha particle and nucleus; scattering is elastic; single scattering (thin target).
What is the mass of a proton?
1.6726 × 10⁻²⁷ kg (0.9383 GeV/c²)
What is the intrinsic parity of a proton?
Even (+1)
Equation for two particles with intrinsic parities P1 and P2 is…
P1 P2 (-1) ^L
L is orbital angular momentum
What does the Dirac eqn predict for g_s for point particles
2
What is the spin g-factor of a proton and neutron?
5.5857
-3.8260837
What does the proton and neutron’s g-factor tell us about its structure?
It is not an elementary particle.
What is the mass of a neutron?
1.6749 × 10⁻²⁷ kg (0.9396 GeV/c²)
What is the intrinsic parity of a neutron?
Even (+1)
Is a free neutron stable?
No, half-life ≈ 886 seconds.
What is the parity operation?
Reflection of spatial coordinates through the origin: (x,y,z) → (−x,−y,−z).
What is even parity?
The wavefunction remains unchanged: ψ(x) = +ψ(−x).
What is odd parity?
The wavefunction changes sign: ψ(x) = −ψ(−x).
How does parity relate between fermions and their antiparticles?
Fermions have opposite parity to their antiparticles.
How does parity relate between bosons and their antiparticles?
Bosons have the same parity as their antiparticles.
Which fundamental forces conserve parity?
Strong and electromagnetic forces.
Which fundamental force violates parity?
Weak force.
What is the magnetic moment associated with orbital angular momentum?
μ = (eħ/2m)l
What is the nuclear magneton?
μₙ = eħ / (2mₚ)
