# I cant solve this MCQ, help please?

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#1
This is a question from June 13 . The answer is B. but how?

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
0
5 years ago
#2
Sorry you've not had any responses about this. Are you sure you’ve posted in the right place? Posting in the specific Study Help forum should help get responses.

I'm going to quote in Puddles the Monkey now so she can move your thread to the right place if it's needed.

Spoiler:
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(Original post by Puddles the Monkey)
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0
5 years ago
#3
(Original post by Fatima SJ)
This is a question from June 13 . The answer is B. but how?

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
As they have the same temperature, the luminosity will depend on the area presented to the observer.
Area depends on radius or diameter squared.
20% greater means x 1.2
1.22 = 1.4 approx.
0
5 years ago
#4
(Original post by Stonebridge)
As they have the same temperature, the luminosity will depend on the area presented to the observer.
Area depends on radius or diameter squared.
20% greater means x 1.2
1.22 = 1.4 approx.
Please refrain from posting full solutions.
0
5 years ago
#5
(Original post by Doctor_Einstein)
Please refrain from posting full solutions.
This is not a full solution to a problem, it is an explanation of why an MCQ answer is what it is.
Educationally, totally different objectives.
2
#6
(Original post by Stonebridge)
As they have the same temperature, the luminosity will depend on the area presented to the observer.
Area depends on radius or diameter squared.
20% greater means x 1.2
1.22 = 1.4 approx.
Thanks alot
0
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