A spectrophotometer is a device that is used to measure the amount of light absorbed by a sample at different wavelengths. A spectrophotometer measures the amount of light that can pass through a sample. It consists of a light source, a sample holder, a diffraction grating or prism to separate the light into its different wavelengths, and a detector to measure the amount of light absorbed at each wavelength.
Spectrophotometry is a standard technique in many chemistry labs. From the data collected, a computer plots an absorbance spectrum for the sample. Spectrophotometry is the action of using a spectrometer to take a measurement.