Study Notes
Stellar radii can be estimated by combining Wien's displacement law and the Stefan-Boltzmann law, which relate a star's temperature, wavelength, luminosity, and radius.
- Wien's Displacement Law — relates a star's surface temperature to the peak wavelength of its emitted light. Example: Higher temperature stars emit shorter wavelength light, appearing blue.
- Black Body — an idealized object that absorbs all radiation and emits radiation based solely on its temperature. Example: Stars are good approximations of black bodies.
- Stefan-Boltzmann Law — relates a star's luminosity to its surface temperature and radius. Example: The energy emitted per unit area is proportional to the fourth power of the temperature.
Exam Tips
Key Definitions to Remember
- Wien's Displacement Law
- Stefan-Boltzmann Law
- Black Body
Common Confusions
- Confusing the peak wavelength with the total energy emitted
- Misunderstanding the relationship between temperature and color of stars
Typical Exam Questions
- How does Wien's Law relate temperature and wavelength? Higher temperature means shorter wavelength.
- What is a black body? An object that absorbs all radiation and emits based on temperature.
- How do you estimate a star's radius? Use Wien’s law for temperature, then Stefan-Boltzmann law for radius.
What Examiners Usually Test
- Understanding of how temperature affects wavelength and color
- Ability to apply Wien's and Stefan-Boltzmann laws to solve problems