IB HL Physics 2025-32 - E1 & E2. Quantum physics and the atom

E1 & E2. Quantum physics and the atom

Guiding questions:

What is the current understanding of the nature of an atom?

What is the role of evidence in the development of models of the atom?

In what ways are previous models of the atom still valid despite recent advances in understanding?

What is meant by wave–particle duality?

Linking questions:

How can emission spectra allow for the properties of stars to be deduced?
How is the distance of closest approach calculated using conservation of energy?
How can emission spectra be used to calculate the distances and velocities of celestial bodies?
Under what circumstances does the Bohr model fail? (NOS)
How have observations led to developments in the model of the atom? (NOS)
How can particles diffract?
What are the defining features and behaviours of waves?
What evidence indicates the diffraction of a wave?
How is photon scattering off an electron similar to and how is it different from the collision of two solid balls?
Can the Bohr model help explain the photoelectric effect? (NOS)
How did the explanation of the photoelectric effect lead to the falsification that light was purely a wave? (NOS)
Why is Compton scattering more convincing evidence for the particle nature of light than that from the photoelectric effect? (NOS)

Understandings:

the Geiger–Marsden–Rutherford experiment and the discovery of the nucleus
nuclear notation (Z, A, X)
that emission and absorption spectra provide evidence for discrete atomic energy levels
that photons are emitted and absorbed during atomic transitions
that the frequency of the photon released during an atomic transition depends on the difference in energy level as given by E = hƒ
that emission and absorption spectra provide information on the chemical composition
the relationship between the radius and the nucleon number for a nucleus and implications for nuclear densities
deviations from Rutherford scattering at high energies
the distance of closest approach in head-on scattering experiments
the photoelectric effect as evidence of the particle nature of light
that photons of a certain frequency, known as the threshold frequency, are required to release photoelectrons from the metal
Einstein’s explanation using the work function and the maximum kinetic energy of the photoelectrons as given by Emax = hƒ–Φ where Φ is the work function of the metal
diffraction of particles as evidence of the wave nature of matter
that matter exhibits wave–particle duality
the de Broglie wavelength for particles as given by λ = h p
Compton scattering of light by electrons as additional evidence of the particle nature of light
that photons scatter off electrons with increased wavelength
the shift in photon wavelength after scattering off an electron.
the numerical discrete energy levels in the Bohr model for hydrogen
that the existence of quantized energy and orbits arise from the quantization of angular momentum in the Bohr model for hydrogen as given by mvr = nh/2π .