help with inverse square law(astronomy)?

[g3ts0m3h03]

1. Inverse Square Law
Planets Alpha, Beta, Gamma, and Delta orbit a star. Alpha is 1 AU from the star. Beta is 2 AU from the star, Gamma is 3 AU from the star, and Delta is 4 AU from the star. From Planet Alpha, the star appears as bright as our Sun. How bright does that star appear from Planets Beta, Gamma, and Delta compared to the star’s brightness on Planet Alpha?



a. The star appears equally bright from all planets

b. The star appears 1/2 as bright as viewed from Beta, 1/3 as bright from Gamma, and 1/4 as bright from Delta

c. The star appears 1/2 as bright as viewed from Beta, 1/4 as bright from Gamma, and 1/6 as bright from Delta

d. The star appears 1/4 as bright as viewed from Beta, 1/9 as bright from Gamma, and 1/16 as bright from Delta

so is it A or b???

[campbelp2002]

D
because 1/2^2 = 1/4, 1/3^2=1/9 and 1/4^2=1/16

[peppermint.plant]

Inverse Square law:

Flux (apparent brightness) ~ 1 / d^2

~ means proportional to (in this case approximately equal to).

d = distance

Example:

Beta is twice as far from the star as Alpha is. Given the inverse square relationship this shouldn't be too difficult for you to figure out.

*Edit*

I am not going to just tell you the answer. I explained the inverse square law, I think very clearly, and now it is up to you to apply it. That is how you learn.

[peppermint.plant]

Inverse Square law:

Flux (apparent brightness) ~ 1 / d^2

~ means proportional to (in this case approximately equal to).

d = distance

Example:

Beta is twice as far from the star as Alpha is. Given the inverse square relationship this shouldn't be too difficult for you to figure out.

*Edit*

I am not going to just tell you the answer. I explained the inverse square law, I think very clearly, and now it is up to you to apply it. That is how you learn.

[Vinnie]

Hi Peppermint,

Thanks for that contribution, that's a great way to answer.

One of the things under discussion at this time is the creation of a board for just this type of thing. ie teachers, students, and interaction of this nature.

Could you keep in touch with the forum? Your input would be highly appreciated.

Vin