I designed and made a measurement apparatus to measure the relative transmittance at known NAs reliably. To investigate the fluorescent yield of the samples a tunable monochromator was utilized to control the wavelength (𝜆) of the excitation light accurately. A tungsten halogen lamp was employed as the main light source of the monochromator and the output light is tunable in the 400-800 nm range (visible spectrum) using a motorized mechanism with a spectral emission band of 6 nm. The transmitted light is collected by a collecting lens system that is connected to a fiber optics system to deliver the light to a spectrograph for decomposition and analysis. The spectrograph is able to measure the absolute and relative intensity of light in the range of 380 − 900 nm with a spectral resolution of 1.2 nm. By combining the spectrograph and the monochromatic light source, the pure relative transmittance and fluorescent emission are measured simultaneously for each illumination wavelength produced by the monochromator.