Apparent Magnitude and Intensity Formula

[thegirl]

Hey,
Could anyone explain why Ia/Ib=2.512^(Mb-Ma), Where "Ia" and "Ib" are intensities of star a and star b and "Mb" and "Ma" are the apparent magnitudes of star A and star B?

I thought the formula would be Ia/Ib=(2.512)^(Ma-Mb) because Ia=2.512^Ma and Ib=2.512^Mb.

Thank You

 

[wabbit]

Magnitude is an "inverse" scale in this sense : magnitude 0 is very bright (about the brightest visible stars), magnitude 10 is very faint (invisible naked eye). There's a minus sign missing in your formulas for la, lb.

 

[thegirl]

Thank you so much! So the actual relative intensity of magnitude 5 is 0.1 relative to the apparent magnitude 0?

Thanks again!

 

[wabbit]

Actually, 0.01 : 2.5^5=~100, the scale is actually defined by the ratio of 100 for a difference of 5.Edit : see https://www.wikipedia.org/wiki/Apparent_magnitude

 

[thegirl]

Thank You!