Calibration Curves: Understanding How to Find Concentration of Unknowns

[BogMonkey]

I looked this up but couldn't find sufficient information on it. What I know is that calibration curves are used to find the concentration of an unknown compound by graphing a series of measurements of a property like light absorbance from standard solutions of that compound. What I don't get is how this graph would be used to find the concentration of unknowns though. Let's say I measure the absorbance of an unknown would I just plug the absorbance value into the curve equation or just find the corresponding x (or y) value? If so is that all they mean when they say calibration curve?

 

[Borek]

My bet is that calibration curve (as a name) was used first in ancient times when it was much easier to plot a curve and then read the result from the curve. You know, before calculators and stuff. Technically that's the same as using curve equation, just much faster and much simpler when you have to do all calculations by hand. Also less accurate, but that's another story.