Answer:
Scratches and fingerprints on the surface of the cell can decrease the amount of light that reaches the detector. If this happens your results will not be accurate.
Step-by-step explanation:
This instrument depends on a careful usage to measure accurately the concentration in an specific solution. The wavelength can be inaccurate if some procedures were not done during the preparation process.
When cleaning the cuvette or manipulating it, always use a lint free cloth and make sure that you removed any drops of water that might have fallen into the cuvette.