A2 -physics a levels astrophysics mcq

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MARYAM1234567
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#1
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#1
α-Centauri is one of the nearest stars to our Sun. The surface temperatures of these two
stars are about the same. α-Centauri has a 20% greater diameter than the Sun.
The ratio of the luminosity of α-Centauri to the luminosity of the Sun is about
A 1.2
B 1.4
C 1.7
D 2.1


the answer is supposed to be B
pls help me out
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Joinedup
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Have you thought about the relative surface area of the stars?
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MARYAM1234567
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#3
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(Original post by Joinedup)
Have you thought about the relative surface area of the stars?
yeah i do know that the formula
L=A x T^4 x (k) ...k=stefan boltzamn constant
where the A =4pi(r^2) and sine all the other things are constant ...L is proportional to the area
but i dont know how to get to the answer using the area
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MARYAM1234567
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#4
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i would really appreciate if you could show me the working of the question...as that would save alot of time
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username3442196
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It looks like you've worked it out ( L prop surface area; area prop radius squared) ...
radius alpha centuri = ....... x radius sun
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MARYAM1234567
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(Original post by old_teach)
It looks like you've worked it out ( L prop surface area; area prop radius squared) ...
radius alpha centuri = ....... x radius sun
i dont get it
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Joinedup
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(Original post by MARYAM1234567)
i dont get it
diameter of α-Centauri = 1.20 diameter of the Sun
1.202=???
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MARYAM1234567
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(Original post by Joinedup)
diameter of α-Centauri = 1.20 diameter of the Sun
1.202=???
i know i'd look very dumb but
how'd you take 1.2 as the diameter..
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Joinedup
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#9
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saying the diameter is 20% greater than that of the sun is identical to saying the diameter is 1.20 times the diameter of the sun.
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