This type of investigation is in accordance with Beer-Lambert law, which shows a linear relationship between the absorbance and the concentration of an absorbing species.
In order to carry this investigation out, a number of samples of the substance being investigated are prepared, each with different concentrations. Then, the transmittance of light through each sample is measured. Finally, the graph between -log(transmittance) and concentration is plotted, to obtain a linear relationship between the two variables.
