Comprehensive Physics: Atomic Structure, Nuclear Forces, Particle Types, and Interactions

Charge and relative mass of a proton

Charge: +1.6 × 10⁻¹⁹ C; Relative mass: 1

Charge and relative mass of an electron

Charge: -1.6 × 10⁻¹⁹ C; Relative mass: 1/1836

Atomic number (Z)

The number of protons in the nucleus.

Mass number (A)

The total number of protons and neutrons in the nucleus.

Specific charge

Specific charge = charge / mass (C/kg)

Isotope

An atom with the same number of protons but different numbers of neutrons.

Range of the strong nuclear force

Repulsive below 0.5 fm, attractive between 0.5 fm and 3 fm.

Need for the strong nuclear force

To overcome electrostatic repulsion between protons and hold the nucleus together.

Alpha decay

Emission of a He-4 nucleus: 2 4 He.

Beta-minus decay

A neutron becomes a proton, emitting an electron and an antineutrino: n→p+e−+νˉe.

Reason for proposing neutrinos

To account for missing energy, momentum, and lepton number in β-decay.

Formula for photon energy

E=hf=λhc.

Constants in the photon energy equation

h=6.63×10⁻³⁴ Js, c=3.00×10⁸ m/s.

Antiparticle

A particle with the same mass but opposite charge and quantum numbers.

Antiparticle of an electron

A positron (e⁺).

Annihilation

A particle and antiparticle collide and produce two photons.

Pair production

A photon turns into a particle-antiparticle pair.

Minimum energy for pair production

E=2mc².

Four fundamental forces

Gravitational, Electromagnetic, Strong Nuclear, Weak Nuclear.

Exchange particles for electromagnetic interaction

Virtual photon (γ).

Exchange particles for weak interaction

W⁺, W⁻, Z⁰.

Exchange particles for strong interaction

Gluon (quarks), Pion (nucleons).

Weak force acts on

All fermions (quarks and leptons).

Strong force acts on

Hadrons (baryons and mesons).

Hadrons

Particles that feel the strong nuclear force and are made of quarks.

Types of hadrons

Baryons (3 quarks) and Mesons (quark + antiquark).

Leptons

Fundamental particles not made of quarks (e.g., electrons, neutrinos).

Baryon number of a proton

1

Baryon number of an antiproton

-1.

Conserved quantities in particle interactions

Charge, baryon number, lepton number, energy, and momentum.

Strangeness conservation

No - only conserved in strong interactions.

Charge of an up quark

+2/3.

Charge of a down or strange quark

-1/3.

Quark content of a proton

uud.

Quark content of a neutron

udd.

Quark content of a π⁺ meson

up quark + anti-down quark (u anti-d).

Quark content of a K⁺ meson

up quark + anti-strange quark (u anti-s).

Apparatus to detect particle tracks

Cloud chambers or bubble chambers.

Inverse square law for gamma radiation

I∝1/r².

Uncertainty in radioactive count rate

N (where N is the number of counts).

Reducing percentage uncertainty in experiments

Use larger readings, repeat measurements, and use precise equipment.

When strangeness can change

In weak interactions only.

Lepton number of an electron neutrino

1

Lepton number of a muon antineutrino

-1 (for muon lepton number).