Ok, so the brightness of a star is supposed to be proportional to the 
luminosity / distance squared.

If a star's luminosity suddenly increases by 600 then the apparent magnitude 
should be +600 (since the distance is unchanged), right?

Yet apparently the correct answer is that the apparent magnitude decreases 
by 7.  Can someone please 'splain?

Thanks.

In message <48249d70$0$15176$607ed4bc@cv.net>, Robert 
 writes
>Ok, so the brightness of a star is supposed to be proportional to the
>luminosity / distance squared.
>
>If a star's luminosity suddenly increases by 600 then the apparent magnitude
>should be +600 (since the distance is unchanged), right?
>
>Yet apparently the correct answer is that the apparent magnitude decreases
>by 7.  Can someone please 'splain?
>
>Thanks.
>
>
Magnitude is a logarithmic scale, not a linear one, and is defined such 
that brighter objects have lower magnitudes. A decrease of 5 magnitudes 
is defined as a 100-fold increase in brightness, i.e. 1 magnitude 
corresponds to a factor of approximately 2.512 in brightness.
-- 
Stewart Robert Hinsley