| Lesson Plan |
| Grade: |
Date: 01/12/2025 |
| Subject: Physics |
| Lesson Topic: use Wien’s displacement law and the Stefan–Boltzmann law to estimate the radius of a star |
Learning Objective/s:
- State Wien’s displacement law and the Stefan–Boltzmann law.
- Derive the formula for a star’s radius in terms of its luminosity and effective temperature.
- Apply the derived formula to calculate stellar radii from given λmax and luminosity data.
- Interpret how temperature influences radius for a fixed luminosity.
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Materials Needed:
- Projector and screen
- Whiteboard and markers
- Scientific calculators or spreadsheet software
- Printed worksheet with star data and constants
- Formula sheet (Wien’s constant, σ, solar values)
- Exit‑ticket slips
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Introduction:
Stars may look like point sources, yet physics lets us estimate their sizes. Students should already recall black‑body radiation and basic algebraic manipulation. Today they will demonstrate they can compute a star’s radius from its peak wavelength and luminosity and explain the temperature‑radius relationship.
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Lesson Structure:
- Do‑now (5'): quick quiz on Wien’s law and the Stefan–Boltzmann law.
- Mini‑lecture (10'): derive R = √[L/(4πσT⁴)] and discuss each term.
- Guided example (10'): work through the Sun calculation step‑by‑step.
- Group activity (15'): using the worksheet, calculate radii for Betelgeuse and an exoplanet‑host star.
- Concept discussion (5'): compare results and relate temperature to radius.
- Check for understanding (5'): exit‑ticket question – “What happens to the radius if temperature doubles while luminosity stays constant?”
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Conclusion:
We reviewed how Wien’s and Stefan–Boltzmann laws combine to give a practical radius estimate and applied it to real stars. Students now complete an exit ticket and are assigned three additional practice problems to reinforce the method at home.
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