PhysicsRelativity & Quantum Physics

Effective Study Strategies

• Understand frame of reference: Inertial frames have zero acceleration; non-inertial frames have acceleration. Earth is approximately inertial for most purposes.
• Master special relativity postulates: (1) Laws of physics are same in all inertial frames. (2) Speed of light is constant in all frames.
• Learn relativistic formulas: Time dilation (t = t₀/√(1-v²/c²)), length contraction (l = l₀√(1-v²/c²)), mass increase (m = m₀/√(1-v²/c²)), and mass-energy equivalence (E=mc²).
• Practice black body radiation concepts: Wien’s displacement law (λ_max T = constant), Stefan-Boltzmann law (E ∝ T⁴), and Planck’s quantum hypothesis (E = hf).
• Understand photoelectric effect thoroughly: Einstein’s equation: hf = φ + K.E_max. Threshold frequency (f₀), work function (φ = hf₀), and stopping potential (V₀e = K.E_max).
• Master wave-particle duality: Light exhibits both wave (diffraction, interference) and particle (photoelectric effect, Compton scattering) nature. De Broglie hypothesis: λ = h/p for particles.
• Learn about pair production and annihilation: Minimum photon energy for pair production is 1.02 MeV. Electron-positron annihilation produces two photons moving in opposite directions.
• Apply Heisenberg uncertainty principle: Δp·Δx ≥ h/4π. Cannot simultaneously measure position and momentum with absolute precision.

Exam Preparation Tips

• Memorize key formulas on flashcards: Relativistic equations, photoelectric equation (hf = φ + K.E_max), de Broglie wavelength (λ = h/p), Compton shift (Δλ = h/(m₀c)(1-cosθ)).
• Practice numerical problems: Calculate relativistic mass, time dilation, length contraction, de Broglie wavelength, photoelectric stopping potential.
• Understand graphical representations: Black body radiation curves, photoelectric current vs voltage, K.E_max vs frequency graphs.
• Differentiate between classical and quantum concepts: Classical physics fails at high speeds (relativity) and atomic scales (quantum mechanics).
• Learn historical experiments: Michelson-Morley (constancy of light speed), Davisson-Germer (electron diffraction), Compton scattering.
• Time yourself on complex problems: Set a timer for 3-4 minutes per problem to simulate exam conditions.

Common Pitfalls to Avoid

• Applying classical formulas at relativistic speeds (v approaching c)
• Confusing work function with threshold frequency (φ = hf₀)
• Forgetting that relativistic effects are negligible at everyday speeds
• Mixing up Compton effect (photon-electron scattering) and photoelectric effect (photon absorption)
• Not recognizing that de Broglie wavelength applies to all matter, not just electrons
• Assuming that uncertainty principle is due to measurement limitations rather than fundamental property
• Confusing pair production (photon → e⁻ + e⁺) with annihilation (e⁻ + e⁺ → photons)