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IB Physics HL E 1 6 Spectra and Composition Questions

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

Syllabus
First assessment 2025
Course
Physics HL
Level
HL

Exam points

  • Determine stellar composition from absorption and emission spectral lines.
  • Explain laboratory comparison and identification of elements in stars and nebulae.
  • Evaluate spectral evidence for hydrogen, helium and other stellar constituents.

IB Physics HL 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 HL E 1 6 Spectra and Composition Questions question 1 — IB Physics HL

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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