Physics A-Level
Luminosity
What Luminosity means in Physics A-Level, as defined for AQA, OCR.
Definitions of Luminosity
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Reference: AQA
How much light an object emits, which apparent magnitude does not describe, so apparent magnitude is not an intrinsic property.
A quantity that may be given or inferred from apparent brightness and distance, and is used in Stefan’s law.
For a given temperature it depends on radius squared, linking position on the diagram to L = 4πR²σT⁴.
Power of about 3.8 × 10²⁶ W for the Sun, which must be multiplied by time to find total energy.
The total electromagnetic power a star radiates in all directions, measured in watts (W).
Topics that use Luminosity
- Classification by luminosity (A-level only) (AQA A-Level)
- Supernovae, neutron stars and black holes (A-level only) (AQA A-Level)
- The Hertzsprung-Russell (HR) diagram (A-level only) (AQA A-Level)
- Electromagnetic radiation from stars (OCR A-Level)
Related terms
- absolute magnitude
- Accretion
- Active galactic nuclei
- Apparent magnitude
- Apparent versus absolute magnitude
- Black hole
- Black-body modelling of stars
- Brightness
Using Luminosity in the exam
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