Linearity of the instrument is checked using which materials?

• A. Neutral density filters and dichromate solution
• B. Gas discharge lamp
• C. Photomultiplier tube
• D. Holmium oxide

Answer: (A)

Linearity means the instrument’s signal should be proportional to how much light the sample absorbs, across a range of intensities and concentrations. Neutral density filters provide known, fixed attenuation of the light reaching the detector, letting you test whether the detector and electronics respond proportionally as the light level changes. By measuring with different filters and verifying that the readings scale consistently, you confirm the system’s linear response to light intensity. Potassium dichromate solutions give absorbance values that, within a certain concentration range, increase linearly with concentration according to Beer’s law. Preparing several known concentrations and measuring their absorbances allows you to verify that the instrument’s response remains linear with concentration. Together, these materials check both the light-path/detector side and the sample side of the measurement, which is why they are used to assess linearity. The other options relate to wavelength calibration or basic components, not to establishing a linear response across a range.