Light is the language of atoms. Because understanding light is crucial for understanding absorbance and emission spectroscopy, we begin this discussion with our students by introducing the nature of light. Light acts as both a particle and wave. When describing light, the term photon is used to emphasize its particle like characteristics. And when characterizing light, we use the wave-like properties of frequency and wavelength to describe the photon. It is a mass-less type of energy, similar in some ways to heat and electricity. It can even promote certain reactions.
Our students are most familiar with light in the visible region (400 and 700 nm), as shown in the following spectrum, mainly due to this range being detectable to our eyes. Wavelengths shorter than 400 nm are called ultraviolet radiation (which causes sunburns) and those longer are infrared (used to in television remotes).
Students can use MicroLab’s Model 141 Visual Spectrophotometer to visualize, calibrate and quantify both absorbance and emission spectra. To understand the relationship between energy, color wavelength and frequency of light, give your students and afternoon with the Model 214 Energy of Light Module. This module allows them to select from a series of visible and IR Light-Emitting Diodes. Then they adjust the voltage and measure the potential required to initiate emission of light for the various LEDs. From this, students visually observe that the shorter wavelength LEDs require a greater voltage, or more energy. This module can be connected to a MicroLab FS 524 interface or as a standalone instrument using a voltmeter.