What is difference between spectrophotometry and spectroscopy?

1 Answer
Mar 25, 2016

You can think of Spectrometry as general study of interaction of matter with electromagnetic waves (the whole spectra). While Spectrophotometry is the quantitative measurement of light spectra reflection and transmission properties of materials as function of the wavelength. Note from first principle perspective you need to have the former for the latter. Think of the former as the foundational component (the physics),and the latter an application of the former for a specific subject of measurement.


Spectroscopy is the study of the interaction between matter and radiated energy (electro magnetic waves). This can be interpreted as the science of studying the interactions of matter and radiation. To understand spectroscopy, one must first understand the electromagnetic spectrum that stretch from Microwaves, Radio waves, Infrared and Ultraviolet rays, X-Rays and Gamma rays . The energy of these waves is dependent on the wavelength or the frequency of the wave. High frequency waves have high amounts of energies, and low frequency waves have low amounts of energies.

If you look at NIST definition of spectrophotometry is states that
" Spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength. While relatively simple in concept, determining the reflectance or transmittance involves careful consideration of the geometrical and spectral conditions of the measurement ."

A spectrophotometer consists of two instruments, namely a spectrometer for producing light of any selected color (wavelength), and a photometer for measuring the intensity of light. The instruments are arranged so that liquid in a cuvette can be placed between the spectrometer beam and the photometer. The amount of light passing through the tube is measured by the photometer. The photometer delivers a voltage signal to a display device, normally a galvanometer. The signal changes as the amount of light absorbed by the liquid changes.