1.Turn on the power of the spectrophotometer and allow it to warm up thoroughly (at least 30 minutes, and in some instruments, it may require 1 hour for stability). During the warm-up time, measure the diameter and length of the sample tube.

2.Prepare a white paper strip approximately 2 cm wide and slightly smaller than the diameter of the sample tube (with sufficient thickness to reflect the incident light from the wavelength selector). Place it inside an empty sample tube.

3.Insert the sample tube into the sample chamber without covering the lid, allowing observation of the monochromatic light reflected from the white paper strip inside the sample tube.

4.Use the wavelength adjustment knob to set the wavelength to approximately 650 nm (or another wavelength with a distinct color), and observe the reflected light inside the sample tube. Adjust the height or rotation of the sample tube to enhance the intensity of the reflected light. If the light is still too weak, use the 100%T adjustment knob.

5.Slowly change the wavelength from 400 to 700 nm using the wavelength adjustment knob. Pay attention to the blue, green, and red lights, and record their wavelength ranges.