|Jan2-10, 03:19 AM||#1|
1. The problem statement, all variables and given/known data
Question 1 - If two stars A of luminosity 9000 and B of luminosity 90 (both relative to the Sun) appear equally bright from the Earth, how much further away is A from B?
Question 2 - Star A is twice as bright as Star B, but B is twice as far away as A. Which star has the greater luminosity, and by what ratio?
Question 3 - If two stars, A and B, are the same distance away, but B is 20 times more luminous than A, how much brighter will B appear than A?
I could use some assistance as to how I should set these out in accordance with
brightness (proportional to) Luminosity / R^2
2. Relevant equations
3. The attempt at a solution
Question 1 - Worked out to - by moving Star A 10 times further away we have diminished the apparent brightness of Star A by a factor 10 x10 = 100 so that it now matches the brightness of Star B.
Question 2 - Worked out to - Luminosity of A
Luminosity of B = (½)2 x 2 = ½
This means that Star A really only has half the luminosity of Star B, but appears brighter because it is closer.
Question 3 - Worked out to 1/20th .
Just need assistance to set these out correctly - and also make sure that they are correct.
|Jan3-10, 02:11 PM||#2|
|Jan3-10, 07:22 PM||#3|
Blog Entries: 10
|Jan3-10, 10:10 PM||#4|
Zebra, you seem to be really close on the last one. When distance is constant, the apparent brightness is just proportional to the luminosity.
|Jan4-10, 12:15 AM||#5|
Many thanks for the replies.
Yes, I think I understand what you are saying about question 3.
Again, many thanks for the replies.
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