The Cary Varian 5000 spectrometer permits to perform optical transmission measurements from 175 to 3300 nm. The experimental setup include transmission measurements on bulk and liquid samples, reflection measurements at fixed (12.5 degree) and Variable Angle Specular Reflectance Accessory (VASRA: 20-70 degree), and an internal integrating sphere for diffuse reflectance measurements (DRA 2500, 200 – 2500 nm).
In spectroscopy, the absorbance A (also called optical density) is defined as A(λ) = - log(Iλ /I0) where I(λ) is the intensity of light at a specified wavelength λ that has passed through a sample (transmitted light intensity) and I0 is the intensity of the light before it enters the sample or incident light intensity (or power). Absorbance measurements are often carried out in analytical chemistry or material science, since the absorbance of a sample is proportional to the thickness of the sample and the concentration of the absorbing species in the sample, in contrast to the transmittance (Iλ /I0) of a sample, which varies logarithmically with thickness and concentration. In a similar manner it is possible to extract the spectral dependence of the real part of the refractive index n(λ).