Quantum Physics

What these notes cover

These notes cover quantum physics for Cambridge International A Level Physics (9702): the photon model of electromagnetic radiation, the photoelectric effect, wave–particle duality and electron diffraction, and energy levels in atoms with emission and absorption line spectra.

Key formulas and definitions

• Photon energy: E = hf = hc/λ
• Photon momentum: p = E/c
• Electronvolt: 1 eV = 1.60 × 10⁻¹⁹ J
• Photoelectric equation: hf = Φ + ½mv²_max, where Φ is the work function.
• Threshold frequency: f₀ = Φ/h
• de Broglie wavelength: λ = h/p
• Energy levels: hf = E₁ − E₂ for a photon emitted or absorbed in a transition between levels.