Inverse Square Brightness Calculator — Formula
## Inverse Square Law
Brightness (flux) decreases with the square of the distance from the source.
**F2 / F1 = (d1 / d2)²**
In magnitudes: **m2 - m1 = 5 log10(d2 / d1)**
Doubling the distance reduces brightness to 25% and increases magnitude by 1.505.
Brightness (flux) decreases with the square of the distance from the source.
**F2 / F1 = (d1 / d2)²**
In magnitudes: **m2 - m1 = 5 log10(d2 / d1)**
Doubling the distance reduces brightness to 25% and increases magnitude by 1.505.
Esempio Risolto
Compare brightness at distances 1 and 2 (same units).
- F2/F1 = (1/2)² = 0.25
- At twice the distance, brightness is 25%.
- Magnitude diff = 5 log10(2) = 5 × 0.301 = 1.505 mag fainter.