Mathieu made three solutions of a chromophoric compound, with concentrations of 0.005 M, 0.010 M, and 0.020 M respectively. He measured the absorbance of each solution in the UV-vis instrument, at a wavelength of 450 nm. For each solution the machine reported the same absorbance value, around 3.950 AU. That can't be right! What is wrong? And, how can Fred change his experiment to fix this problem?

Note that you can assume Fred did everything right in the lab: he used a blank solution correctly; the UV-vis instrument was working perfectly; the quartz cuvettes that he used were all perfectly clean. The problem is clearly and explicitly indicated by the information provided. It isn't a complicated scenario, and a brief one- or two-sentence answer would be sufficient.

Please need help asap. Thank you