Calcolatore Luminosita Inverso del Quadrato
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Brightness Ratio (F2/F1)
0.250000
Brightness Ratio (F2/F1) vs Distance 1
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.
Esempio Risolto
Compare brightness at distances 1 and 2 (same units).
- 01F2/F1 = (1/2)² = 0.25
- 02At twice the distance, brightness is 25%.
- 03Magnitude diff = 5 log10(2) = 5 × 0.301 = 1.505 mag fainter.
Domande Frequenti
Why does the inverse square law work?
Light spreads uniformly over a sphere. The sphere's area grows as 4πr², so intensity per unit area decreases as 1/r².
Does this apply to all radiation?
Yes, for any point source of radiation in a vacuum, including light, radio, X-rays, and gravitational radiation.
How far away does a star need to be for its light to be negligible?
It depends on the star's luminosity and your detector sensitivity. The Sun would be invisible to the naked eye beyond about 20 parsecs.