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Topic 3: Light and Atoms

7 dot points, in syllabus order. Each dot point has a focused answer, with exam-style questions and worked answers where available.

Why do atoms emit and absorb light only at specific wavelengths, and how does the Bohr model explain this?

Explain atomic emission and absorption spectra using the Bohr model and the relationship between photon energy and energy-level differences.

How discrete atomic energy levels in the Bohr model produce line emission and absorption spectra, and the link between photon energy and the difference between energy levels.

9 min read →

Why can't the wave model explain the photoelectric effect, and what does it reveal about the nature of light?

Explain the photoelectric effect using the photon model, including threshold frequency, work function and maximum kinetic energy.

Why the photoelectric effect contradicts the wave model, Einstein's photon explanation, and the photoelectric equation linking photon energy, work function and electron kinetic energy.

9 min read →

What are the fundamental building blocks of matter, and how does the Standard Model organise them?

Describe the Standard Model classification of fundamental particles into quarks, leptons and force-carrying bosons.

How the Standard Model classifies matter into quarks and leptons, how quarks build protons and neutrons, the role of force-carrying bosons, and antimatter.

9 min read →

What evidence shows that light behaves as a wave, and how do waves combine when they overlap?

Describe the wave model of light and apply the principle of superposition to constructive and destructive interference.

The wave model of light, the principle of superposition, and how path difference determines constructive and destructive interference, with worked examples.

9 min read →

Why are some nuclei unstable, and how do they decay and change over time?

Describe alpha, beta and gamma decay, balance nuclear equations, and apply the concept of half-life.

The structure of the nucleus, the three types of radioactive decay, writing balanced nuclear equations, and using half-life to describe decay over time, with worked examples.

9 min read →

What is a photon, how is its energy related to frequency, and what does this mean for the dual nature of light?

Apply the photon model to calculate photon energy and explain wave-particle duality.

The photon as a quantum of light energy, the relationship $E = hf$ using Planck's constant, the electronvolt, and the idea of wave-particle duality, with worked examples.

9 min read →

How does Young's double-slit experiment confirm the wave nature of light and let us measure its wavelength?

Analyse the double-slit interference pattern and use the fringe-spacing relationship to determine wavelength.

Young's double-slit experiment, why it produces evenly spaced bright and dark fringes, and the relationship linking fringe spacing, wavelength, slit separation and screen distance.

9 min read →