BRAINCAKEThe Inverse Square Law for Intensity
A star radiates its power equally in all directions. At a distance d from the star, that power L is spread over the surface of a sphere of area 4πd2. The intensity received is therefore
I = L ÷ 4πd2
This is an inverse square law: I is proportional to 1/d2. Doubling the distance spreads the same power over four times the area, so the intensity falls to a quarter. Tripling the distance reduces it to a ninth.
Sign in free to see the rest of this lesson, the R.E.C.I.P.E. recall steps and the quiz
BrainCake is free. Make an account in seconds and pick up where this page stops.
More in Space
- Black-Body Radiation
- Stefan-Boltzmann Law
- Wien's Law
- Luminosity and Intensity
- Estimating Stellar Radius and Temperature
- The Hertzsprung-Russell Diagram
- Formation of a Star
- Life Cycle of a Star
All 18 lessons in Space · All Edexcel A-level Physics topics