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VICPhysicsQuick questions
Unit 4: How have new ideas and ways of thinking developed our understanding of the physical world?
Quick questions on Atomic energy levels and emission spectra: VCE Physics Unit 4
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is forgetting the sign of energy levels?Show answer
$E_n$ is negative (bound state). Transitions emit photons with positive energy $E_i - E_f$ (since $E_i > E_f$ for a downward transition, both being negative, $E_i - E_f$ is the smaller magnitude minus the larger, giving positive).
What is wrong direction of transition?Show answer
Photon emission requires a downward transition (higher to lower level). Absorption requires an upward transition.
What is trying to absorb arbitrary photons?Show answer
Only photons whose energy matches a transition can be absorbed. A 5 eV photon cannot be absorbed by ground-state hydrogen (it would require a 5 eV transition; the smallest hydrogen transition from $n=1$ is 10.2 eV).
What is using kinetic energy instead of photon energy?Show answer
The photon energy is $E_{\text{photon}} = h f$. The energy of the electron after a transition is different (the atom keeps the difference).
What is confusing levels with shells?Show answer
The principal quantum number $n$ corresponds to shells in the Bohr model. In modern quantum mechanics there are sub-levels (s, p, d, f) within each shell; VCE Physics Unit 4 uses the Bohr-level picture.
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