the._.B O N D._.007Jul 2, 2026
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25 Astronomy and cosmology
25.1 Standard candles
Candidates should be able to:
1 understand the term luminosity as the total power of radiation emitted by a star
2 recall and use the inverse square law for radiant flux intensity F in terms of the luminosity L of the source
F = L/(4πd2
)
3 understand that an object of known luminosity is called a standard candle
4 understand the use of standard candles to determine distances to galaxies
25.2 Stellar radii
Candidates should be able to:
1 recall and use Wien’s displacement law λmax ∝ 1/T to estimate the peak surface temperature of a star
2 use the Stefan–Boltzmann law L = 4πσr
2
T4
3 use Wien’s displacement law and the Stefan–Boltzmann law to estimate the radius of a star
25.3 Hubble’s law and the Big Bang theory
Candidates should be able to:
1 understand that the lines in the emission and absorption spectra from distant
