 (A) defined as A=log(P initial/P) where P initial is the radiant power of light striking the sample on one side and P is the radiant power emerging from the other side. Also called optical density 

 a graph of absorbance or transmittance of light versus wavelength, frequency, or wavenumber 

 relates the absorbance (A) of a sample to its concentration (c), pathlength (b), and molar absorptivity (a), A=abc 

 a graph showing the value of some property versus concentration of analyte. when the corresponding property of an unknown is measured, its concentration can be determined from the graph 

 a cell with transparent walls used to hold samples for spectrophotometric measurements 

 the factor used to multiply the initial concentration of reagent to find the diluted concentration 

 the constant of proportionality in Beer’s Law; A=abc (A is absorbance, a is molar absorptivity, b is pathlength, and c is the molarity) 

 in a broad sense, any method using light to measure chemical concentrations 

 (T), defined as T = P/P initial were P initial is the radiant power of light emerging from the other side of the sample 

 distance between consecutive crests of a wave 
