Quantum physics

About this lab: Quantum physics

Interactive simulation for Cambridge A Level Physics 9702 topic 22 Quantum physics: a beam of photons with E = hf = hc/λ, momentum h/λ and the E-f graph whose gradient is h, the photoelectric effect for six metals with the threshold frequency, KE_max = hf − Φ, intensity and a stopping potential, electron diffraction through graphite with the de Broglie wavelength λ = h/mv shrinking the rings as the p.d. rises, and the hydrogen energy levels with emission and absorption transitions, the Balmer lines and the ionisation energy.

Photons and E = hf, the photoelectric effect with work function and stopping potential, electron diffraction and the de Broglie wavelength, and energy levels with line spectra

Quantum physics is a free, browser-based simulation for Cambridge International AS & A Level Physics 9702 (topic 22 Quantum physics). The course is assessed in Paper 1 (multiple choice), Paper 2 (AS structured), Paper 3 (advanced practical), Paper 4 (A Level structured) and Paper 5 (planning, analysis and evaluation). There are 4 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.

Syllabus coverage

• 22.1 Energy and momentum of a photon: EM radiation as particulate; photon as a quantum; E = hf and the electronvolt; Photon momentum: p = E ÷ c. Lessons: Energy and momentum of a photon.
• 22.2 Photoelectric effect: Emission of photoelectrons from illuminated metals; Threshold frequency and threshold wavelength; Work function and Einstein's equation: hf = Φ + ½mv²_max; KE_max independent of intensity; current ∝ intensity. Lessons: The photoelectric effect.
• 22.3 Wave-particle duality: Photoelectric effect vs interference and diffraction; Electron diffraction as evidence for wave nature; de Broglie wavelength: λ = h ÷ p. Lessons: Wave-particle duality.
• 22.4 Energy levels in atoms and line spectra: Discrete electron energy levels in isolated atoms; Formation of emission and absorption line spectra; hf = E₁ − E₂. Lessons: Energy levels and line spectra.

Full syllabus map: A Level Physics 9702 topic 22.

How to use this simulation

1. 1. The photon.
2. 2. Photoelectric effect.
3. 3. Wave-particle duality.
4. 4. Energy levels and spectra.
5. The buttons at the end of the tab strip give the scene the whole window (Full screen, Hide controls) and, on a dark stage, a projector-friendly palette (Light scene). Many scenes also have drag handles: drag them to change the set-up directly.

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