# Ratio calculation

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#1

I tried to use L= 4 pi r^2 o T^4
so dividing them to find the ratio
we will be left with r^2 / r^2
and since diameter increased by 0.2, then the radius will also increase by 0.2
so what i did is just 0.2 x 0.2 = 0.04
Where did i go wrong here?
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6 years ago
#2
(Original post by Daniel Atieh)

I tried to use L= 4 pi r^2 o T^4
so dividing them to find the ratio
we will be left with r^2 / r^2
and since diameter increased by 0.2, then the radius will also increase by 0.2
so what i did is just 0.2 x 0.2 = 0.04
Where did i go wrong here?
If alpha centauri is 20% larger in diameter it is indeed 20% larger in radius.
So the ratio of the radius of apha centauri to that of the Sun is 1.2/1.0 (or 120/100)
The luminosity depends on radius squared, as you correctly state.
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