Quick Revision (30 Minutes)
Night before exam? Morning of exam? This is your救命稻草 (lifeline).
- Read One-Page Summary: 5 minutes
- Review Formula Sheet: 10 minutes
- Practice Flashcards: 10 minutes
- Checklist: 5 minutes
Total: 30 minutes. Complete chapter revision.
📄 One-Page Summary
Particle Nature of Light
- Photon: Quantum of light, E = hν = hc/λ, p = h/λ
- Rest mass: Zero, Speed = c always
- Planck's constant: h = 6.626×10⁻³⁴ J·s
Photoelectric Effect
- Definition: Emission of electrons when light falls on metal
- Einstein's equation: KE_max = hν - φ
- Work function φ: Minimum energy to remove electron, φ = hν₀ = hc/λ₀
- Stopping potential: eV₀ = KE_max
- Key insight: Frequency decides IF, Intensity decides HOW MANY
Wave Nature of Matter
- de Broglie wavelength: λ = h/p = h/(mv)
- For accelerated charge: λ = h/√(2mqV)
- For electron: λ = 12.27/√V Å
- Proof: Davisson-Germer experiment (electron diffraction)
Key Failures of Wave Theory
- Can't explain threshold frequency existence
- Can't explain instantaneous emission
- Can't explain KE independence from intensity
📋 Formula Dump (Memorize These)
Energy & Momentum
p = h/λ = E/c
Photoelectric Effect
eV₀ = KE_max
φ = hν₀ = hc/λ₀
de Broglie Wavelength
λ = h/√(2mKE)
λ = h/√(2mqV)
Shortcuts
λ_e = 12.27/√V Å
h/e = 4.14×10⁻¹⁵ V·s
Constants (Must Remember)
| Constant | Symbol | Value |
|---|---|---|
| Planck's constant | h | 6.626×10⁻³⁴ J·s = 4.14×10⁻¹⁵ eV·s |
| Speed of light | c | 3×10⁸ m/s |
| Electron charge | e | 1.6×10⁻¹⁹ C |
| Electron mass | m_e | 9.1×10⁻³¹ kg |
| Proton mass | m_p | 1836 m_e |
| hc (shortcut) | - | 1240 eV·nm |
🧠 Flashcards
Click card to flip | Use arrow buttons to navigate
What is photoelectric effect?
✅ Pre-Exam Checklist
Concepts (Must Know)
- ☐ Can explain why wave theory fails for photoelectric effect
- ☐ Understand one-photon one-electron concept
- ☐ Know difference between frequency and intensity effects
- ☐ Can explain wave-particle duality
- ☐ Understand why macroscopic objects don't show wave nature
Formulas (Must Memorize)
- ☐ E = hν = hc/λ
- ☐ KE_max = hν - φ
- ☐ eV₀ = KE_max
- ☐ λ = h/p = h/(mv)
- ☐ λ = h/√(2mqV) for accelerated charge
- ☐ hc = 1240 eV·nm (shortcut)
- ☐ λ_e = 12.27/√V Å (for electron)
Problem Types (Must Practice)
- ☐ Work function from threshold wavelength
- ☐ Stopping potential calculation
- ☐ de Broglie wavelength for accelerated particle
- ☐ Comparison of wavelengths (same KE/p/v)
- ☐ Graph interpretation (V₀ vs ν)
- ☐ Threshold frequency problems
Common Mistakes (Must Avoid)
- ☐ Confusing V₀ (volts) with KE_max (eV)
- ☐ Forgetting to check threshold condition
- ☐ Using λ = h/mv for accelerated charge (use λ = h/√(2mqV))
- ☐ Saying photon has mass (rest mass is ZERO)
- ☐ Missing unit conversions (nm to m, Hz to s⁻¹)
🎯 Memory Tricks & Mnemonics
WAVV Rule
Wave theory → All frequency → Violated → Verdict: WRONG
Wave theory predicts emission at all frequencies. This is violated. Wave theory is wrong.
FIF Rule
Frequency decides IF photoelectric effect occurs
Intensity decides Flux (how many electrons)
Same λ → Same P
If de Broglie wavelength is same, momentum is same (λ = h/p)
Then: KE ∝ 1/m, v ∝ 1/m
1240 Magic Number
hc = 1240 eV·nm
Wavelength in nm → Energy in eV: E = 1240/λ
Most valuable number for this chapter!
⚡ Last-Minute Exam Tips
Read this, don't practice problems:
- Review formula sheet above (5 min)
- Go through flashcards (10 min)
- Read common mistakes list (5 min)
- Close eyes, visualize problem-solving steps (5 min)
- Deep breath, confident mindset (5 min)
First 2 minutes of exam:
- Write down hc = 1240 eV·nm on rough sheet
- Write λ_e = 12.27/√V Å
- Write KE_max = hν - φ, eV₀ = KE_max
Having these visible saves mental load during problem-solving.
You've prepared well. Trust your preparation.
This chapter is scoring. Don't overthink.
If you remember:
- Photoelectric: KE_max = hν - φ
- de Broglie: λ = h/p
- hc = 1240 eV·nm
You can solve 90% of problems. Go ace it! 🚀