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I've been given the inverse square law

$$F= L / (4 π d^2)$$

and told to compare the brightness of two stars by taking the ratio of the inverse square law for Star 1 (with quantities $F_1, L_1$, and $d_1$) and Star 2 (with quantities $F_2, L_2$, and $d_2$).

What does it mean to take the ratio of the law for two different values?

hardmath
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True Gret
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  • The ratio means a relationship between two numbers indicating how many times the first number contains the second. – user217519 Apr 22 '16 at 02:43
  • @TrueGret : You have comments and an answer, which I hope you find useful. Can you accept an answer so that it is closed? This is customary on the website. Thank you. –  Apr 25 '16 at 09:05

1 Answers1

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Obtain an expressions for either $\frac{{{F_2}}}{{{F_1}}}$ or $\frac{{{F_1}}}{{{F_2}}}$. The ratio expresses the relative magnitude of stellar brightness. Usually choose the first if ${F_2} > {F_1}$. Forming the ratio eliminates the constant $4\pi $.