平方反比亮度计算器
使用此平方反比亮度计算器快速获得准确的计算结果。
Brightness Ratio (F2/F1)
0.250000
Brightness Ratio (F2/F1) vs Distance 1
公式
## 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.
计算示例
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.
常见问题
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.