The basic working principle of a spectrophotometer involves the following steps: 

• Light Source: The spectrophotometer emits a beam of light, typically from a stable source such as a tungsten filament lamp or a deuterium lamp for UV light. 
• Monochromator: The light beam is then directed through a monochromator, which selects a specific wavelength of light from the broad spectrum emitted by the light source. The monochromator ensures that only light of the desired wavelength reaches the sample. 
• Sample Chamber: The selected wavelength of light is then passed through the sample solution contained in a cuvette or a sample holder. The sample may absorb some of the light depending on its composition and concentration.
• Detector: On the other side of the sample chamber, a detector measures the intensity of the light that passes through the sample. This measurement is typically recorded as a percentage of the light absorbed by the sample relative to the incident light. 
• Data Analysis: The spectrophotometer's software processes the data collected by the detector and presents it in a readable format, often as a spectrum showing the absorption of light at different wavelengths. Researchers can then analyze this data to determine the concentration of specific substances in the sample based on known absorption characteristics.