Modern Physics unit test
A test on this unit alone, marked as a percentage and a letter grade — for the test your class is actually sitting, rather than for May. Answer everything, then submit once: seeing the answer to question 3 before attempting question 4 makes the final percentage meaningless.
Conservation in nuclear reactions
Intensity versus frequency
Energy level transitions
Alpha versus beta decay
Why intensity does not eject electrons below threshold
Photon energy
Compton scattering
What is conserved in a nuclear equation
Decay is random
The 1240 eV·nm shortcut
Ionization energy
Stopping potential
Short answer 1. Define or explain: Evidence for wave-particle duality
3 ptsShort answer 2. Define or explain: Fission vs fusion
3 ptsShort answer 3. Define or explain: Electron diffraction
3 ptsShort answer 4. Define or explain: de Broglie wavelength
3 ptsFree response
12 ptsTRANSLATION BETWEEN REPRESENTATIONS (Question 2, 12 points). Figure 1 shows the energy levels of a hypothetical atom: n = 1 at −5E0, n = 2 at −3E0, and n = 3 at −2E0. For C–D: a device can emit monochromatic electromagnetic radiation whose wavelength λ can be varied continuously. Photons with wavelength λ0 have energy 4E0. (Figure 2 provides axes of photon energy E versus λ for λ0 < λ < 4λ0.)
A. Describe all possible atomic transitions on the Figure 1 diagram that could result in the emission of a photon (each as an arrow between states).
B. Derive an expression for the wavelength of the highest-energy photon that can be emitted from the atom, in terms of E0 and physical constants, as appropriate.
C. Describe the curve of emitted-photon energy E as a function of λ for λ0 < λ < 4λ0 on Figure 2, given that photons of wavelength λ0 have energy 4E0.
D. A student claims that, based on the energy states in Figure 1, the atom can emit a photon of wavelength λ0 and energy 4E0 like the device in part C. Indicate whether the claim is correct or incorrect, and briefly justify by referencing the representation in part A.