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IB Physics SL E 1 6 Spectra and Composition Questions

Use SL stellar spectra to identify chemical composition, matching absorption lines with laboratory spectra and explaining what star light reveals.

Syllabus
First assessment 2025
Course
Physics SL
Level
SL

Exam points

  • Use stellar absorption and emission spectra to identify chemical composition.
  • Explain how spectral lines are matched with laboratory element spectra.
  • Interpret stellar and nebular spectra as evidence for elements and stellar properties.

IB Physics SL E 1 6 Spectra and Composition Questions question 1

[Maximum number: 2]

The diagram shows a simplified energy-balance model for the Earth surface–atmosphere system.

Figure for Question IB Physics SL E 1 6 Spectra and Composition Questions question 1 — IB Physics SL

The following data are given:

 Average albedo of Earth =0.30 Average global temperature of the surface =288 K Average Earth-Sun distance =1.5×1011 m\begin{aligned} \text { Average albedo of Earth } & =0.30 \\ \text { Average global temperature of the surface } & =288 \mathrm{~K} \\ \text { Average Earth-Sun distance } & =1.5 \times 10^{11} \mathrm{~m} \end{aligned}

The primary energy source of the Sun is the proton-proton (p-p) chain of fusion reactions. Four protons and two electrons produce a helium nucleus together with neutrinos and gamma photons. The overall reaction is:

411p+2−10e→24He+200ve+4γ4{ }_{1}^{1} \mathrm{p}+2{ }_{-1}^{0} \mathrm{e} \rightarrow{ }_{2}^{4} \mathrm{He}+2{ }_{0}^{0} v_{e}+4 \gamma

Outline how the presence of helium in the Sun can be confirmed empirically.

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