State the charge of an electron in terms of the elementary charge.

What does charge quantization mean?

Why was Rutherford scattering evidence for a small nucleus?

State the rest-energy relation used in particle physics.

What minimum energy is required to create an electron-positron pair?

Explain why the positron was interpreted as the electron's antiparticle.

Why was the neutrino proposed in beta decay?

A photon of energy \(3.00\,\mathrm{MeV}\) creates an electron-positron pair. Estimate the kinetic energy shared by the pair if the recoil is negligible.

Why did cloud chambers and bubble chambers matter historically?

A particle track bends in the opposite direction to a proton track in the same magnetic field. What can be inferred?

Explain how conservation laws guide particle discovery.

Why is pair production impossible for a single photon in empty space?

Compare the historical roles of the electron and proton discoveries.

A neutral particle leaves no direct track but decays into two charged tracks. Why can it still be detected?

Why did the discovery of the muon complicate a simple proton-neutron-electron picture of matter?

A proposed decay is \(X^0\to e^-+e^-\). Use charge conservation to test it.

A new charged particle has the same mass as a known particle but opposite charge and opposite lepton number. What interpretation is likely?

How did the quark model simplify the growing list of hadrons?

Why is rest energy important when interpreting high-energy collisions?

A detector sees missing transverse momentum after a collision. Give a particle-physics interpretation and a caution.