Overview
This lecture covers the key principles of waves, forces, energy, electricity, particle physics, and related equations, focusing on definitions, formulas, and core concepts useful for exams.
Waves: Types, Properties, and Behavior
- Waves transfer energy without transferring matter.
- Transverse waves: particles oscillate perpendicular to energy transfer (e.g., light, EM waves).
- Longitudinal waves: particles oscillate parallel to energy transfer (e.g., sound).
- Wavelength (λ): distance between two peaks; Amplitude: max displacement; Time period (T): time for one complete wave.
- Frequency (f): number of waves per second; f = 1/T.
- Wave speed (v): v = fλ.
- Polarization occurs only in transverse waves, with filters allowing specific oscillation directions.
- Superposition/interference: overlapping waves sum displacements; nodes (no energy), anti-nodes (energy transferred).
- Young's Double Slit: creates interference patterns; W = λD/s (fringe spacing).
- Diffraction grating: nλ = d sinθ; maximum order when θ = 90°.
Forces, Motion, and Energy
- Newton's First Law: motion constant without external force.
- Second Law: F = ma (force = mass × acceleration).
- Third Law: every action has equal and opposite reaction.
- Weight: w = mg.
- Equilibrium: zero resultant force and moment.
- Kinetic energy: KE = ½mv²; Gravitational potential energy (GPE) = mgh.
- Work done: W = Fd (force × distance); Power: P = Fv.
- Hooke’s law: F = kx (spring force); energy stored = ½kx².
- Stress = F/A; Strain = ΔL/L₀; Young’s modulus = stress/strain.
Electricity and Circuits
- EMF: energy supplied per coulomb by a battery.
- Ohm’s Law: V = IR (voltage = current × resistance).
- Series circuits: same current, voltage shared; Parallel: same voltage, current shared.
- Total resistance (series): Rₜ = R₁ + R₂; (parallel): 1/Rₜ = 1/R₁ + 1/R₂.
- Power: P = IV, P = I²R, or P = V²/R.
- Resistivity: ρ = RA/L.
- Internal resistance: ε = V + Ir.
- Kirchhoff's Laws: Current into a junction = current out; EMFs equal total PD drops in a loop.
Particle Physics
- Matter: hadrons (baryons and mesons, made of quarks) and leptons (fundamental, e.g., electrons).
- Four forces: electromagnetic (virtual photon), strong (pion), weak (W±), gravity (graviton).
- Strong force: attractive at short range, repulsive at very close range.
- E = mc² links mass and energy.
- Annihilation & pair production: particle ↔ photon conversions.
Quantum Phenomena & Radioactivity
- Photoelectric effect: ejected electrons when photons hit metal; KE_max = hf − Φ.
- Stopping potential: eV = KE_max.
- de Broglie wavelength: λ = h/p.
- Alpha decay: helium nucleus emission; Beta decay: electron emission + antineutrino; Gamma: high-energy photon.
- Conservation laws: charge, baryon number, lepton number always conserved.
Key Terms & Definitions
- Transverse wave — oscillate perpendicular to energy direction.
- Longitudinal wave — oscillate parallel to energy direction.
- Wavelength (λ) — distance between corresponding points on consecutive waves.
- Frequency (f) — complete waves per second.
- Amplitude — maximum displacement from equilibrium.
- Node/Antinode — point of no movement/maximum movement in standing waves.
- Work function (Φ) — minimum energy to liberate an electron from metal.
Action Items / Next Steps
- Review and memorize all key formulas and definitions.
- Practice applying wave, force, energy, and circuit equations to example problems.
- Complete any assigned textbook readings on waves, electricity, and particle physics.