Spectroscopy is the study of how materials react to radiated energy. Light is a radiated energy. Most of the spectrometers Cole-Parmer carries utilize light as the radiated energy source. “Light” exceeds the visible spectrum of color the human eye can see. As shown in the chart below, visible/white light breaks down into separate and unique colors: red, orange, yellow, green, blue, indigo and violet. These colors, and what the human eye can see, are a very small and limited range of the electromagnetic spectrum of radiated energies.
When visible light shines on a blue shirt, the dye in the shirt reflects the blue light and absorbs all the other colors we can see. This is a simple example of how a material, such as a shirt, reacts to light. Over time, the dye may wash out and its concentration in the fabric lessens. The loss in dye concentration can be seen as the color appears lighter and lighter. If looking at the shirt using a spectrometer set to the blue wavelength range, the transmittance (the transmission of radiant energy) would be increasing, and the absorbance (light-absorbing ability) decreasing. The law that surrounds spectroscopy is called “Beer’s Law” written commonly as
A = ε l c
“A” stands for absorbance, “ε;” for Molar absorptivity (also known as the extinction coefficient), “l” represents the pathlength, and “c” is concentration
All spectrometers are based on this law in one way or another. Given the equation, absorption is directly correlated to the extinction coefficient, pathlength, and concentration. If any of the variable on the right-hand side of the equation increases, absorbance will also increase.
Be the first to comment on "Seeing the Light: An Overview of Visible and UV-VIS Spectroscopy"