The BPW21 sensor is a photodiode that is commonly used for light detection rather than measuring the specific wavelength of light. It can detect a broad range of light wavelengths, including visible and near-infrared regions. However, it does not provide direct wavelength measurement capabilities.
To measure the wavelength of light accurately, you would typically require a spectrometer or a device specifically designed for wavelength analysis, such as a monochromator or a spectrophotometer. These instruments use diffraction gratings or other methods to disperse light into its component wavelengths and measure the intensity at each wavelength.
If you are interested in measuring the wavelength of light, it would be more appropriate to use a dedicated wavelength-measuring device or consult an instrument suitable for your specific application.