Physics A-Level
Stefan's law
What Stefan's law means in Physics A-Level, as defined for AQA, OCR.
Definitions of Stefan's law
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Reference: AQA
A black body radiates power P = σAT⁴, where σ is the Stefan constant, A is surface area and T is absolute temperature in kelvin.
States L = 4πr²σT⁴, where r is stellar radius in metres and T is surface temperature in kelvin.
Gives total power per unit area as P/A = σT⁴, so a star of radius r radiates L = 4πr²σT⁴.
L = 4πr²σT⁴, which relates luminosity, radius and temperature.
Topics that use Stefan's law
- Classification by temperature, black-body radiation (A-level only) (AQA A-Level)
- Electromagnetic radiation from stars (OCR A-Level)
Related terms
- Peak wavelength
- Stefan constant
- Wien's displacement law
- Black body
- Black-body modelling of stars
- Continuous spectrum
- Discrete energy levels
- Emission line spectrum
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