Let's assume that you are an educator - high school or college - and you want your students to experience the interaction of light with matter.  Until now, this has not been an easy task. You can give them a diffraction grating or a cardboard spectroscope to observe the emission spectra from various sources and ask them what they see. If your students are like mine were, you will almost certainly have several who see nothing at all - you can only hope that they tell you rather than go along as if they can see the spectrum. Those who do tell you that they aren't seeing anything require some trouble shooting: is the grating oriented properly for observation? Is the slit properly aligned with the grating? Are they looking in the right place so they can actually see the spectral lines? Has someone lost the grating from the spectroscope? It can be a frustrating session.

The new Visual Spectrometer (patent pending) from MicroLab is an inexpensive, rugged teaching tool that takes the guess work and the frustration out of observing emission and absorption spectra.

The view of a continuous white light source through the Visual Spectrometer eyepiece. Photo was taken with a digital camera and the optional Model 143 Camera Mount Accessory.

He lamp emission spectrum as seen to the right of the slit. Photo was taken with a digital camera and the MicroLab Model 143 Camera Mount Accessory.

Students can show you what they see - the eyepiece easily accommodates a digital camera or smart phone so they can show you exactly what they are seeing. As an instructor, you can use a camera in a lecture demonstration to demonstrate emission spectra. (The right webcam can be used, but most webcams do not process color as well as a camera in a smart phone.) 

Optional Model 143 Camera Mount Accessory shown with camera attached (camera is not included). The attachment allows the camera to be aligned with the Visual Spectrometer using included clamps and metal rods and attached to a ring stand support.

Students can see the missing colors!  It has not been easy, or even possible, for students to see visually which colors of light are being removed by the sample. Sure, you can show a graphical display from an expensive spectrometer or a meter readout on a colorimeter, but can your students actually relate the display to what is going on with the light? Most students think in terms of light transmission: if you show a student a purple solution, he or she is likely to explain it in terms of purple light being transmitted rather than red and blue light being transmitted and the middle of the spectrum being absorbed by the sample in solution.  

Visual Spectrometer view of a purple KMnO4 solution showing the missing colors from the middle of the spectrum. The source is an incandescent lamp. The unattenuated source spectrum is viewed immediately below the KMnO4 sample spectrum, allowing the viewer to see immediately which colors are absorbed by the sample.

MicroLab's Visual Spectrometer is an ingenious and easy to use device for seeing exactly what portion of the visible spectrum is being removed by the sample. Simply put a vial of the colored sample into the integrated sample compartment, point it at the source, and observe. The placement of the vial relative to the light transmission allows the observer to see both the unattenuated spectrum of the source (the "reference" spectrum) and the spectrum that is transmitted by the sample.    

This is the eyepiece view of a vial of yellow food coloring in the sample compartment, illuminated with an incandescent lamp source. The source spectrum is seen by the viewer displayed immediately below the sample spectrum, allowing the viewer to see immediately which colors are absorbed by the sample.

The Visual Spectrometer makes a great Distance Learning tool. The relatively low cost of the Visual Spectrometer and its ease of use combine to make it a great addition for home use in distance learning. Students can use diluted food coloring, ink, or vegetable extracts to safely relate spectral properties to colors. They can use it to observe the emission spectra of incandescent and fluorescent lights, LEDs, candles, "cold light" glow sticks, and other light sources.

Students can use MicroLab's Model 245 Spectrophotometer Module and the MicroLab Visual Spectrometer to make a functional, low-cost single wavelength spectrophotometer.   This module provides an adjustable, regulated power supply for the LED's. Output may be read on MicroLab's FS-522 interface, other manufacturers' data loggers that will read voltage, or even a digital voltmeter.  Five plug-in LED assemblies ranging from 880 nm to 400 nm and a modular sensor are provided with the kit. These connect to the photometer module with common "RCA" audio cables. The module is powered by a 9-volt battery. The "100%T" controls set the voltage applied to the LED, setting light level at the LED instead of changing sensor gain, emulating a Spectronic-20.

Model 245 Spectrophotometer Module, which converts the Visual Spectrometer into a single wavelength battery operated electronic colorimeter. It comes with easily interchangable LEDs of 400, 502, 595, 635, and 880 nm and a photodetector. It also comes with RCA cables to make necessary connections. It allows the user to adjust the LED intensity through a blank solution to 100%T and to output the measured %T on samples as a 0-1 volt analog signal.

Students can use the Model 245 to determine the band-gap energy of several LED's by observing the voltage required to initiate emission of light. They can relate energy to color and wavelength and can make a reasonable estimate of Planck's Constant. 

Students can use the Visual Spectrometer and the Model 245 Spectrophotometer Module to explore fluorescence. Samples of chlorophyll or quinine water can be excited with the 400 nm LED. Students can vary the intensity of the light from the LED and see the effect on the fluorescence intensity. They can also observe easily the effect of changing the excitation wavelength by swapping the 400 nm LED for other LEDs in the kit.

Students can use the Visual Spectrometer in conjunction with MicroLab's FS-522 built in FAST-spec(TM) 360-935 nm scanning spectrophotometer to enhance learning. The figure below shows the Beer's Law plot obtained with the soon to be released version 5.8.0 MicroLab software to control the FAST-spec spectrometer on the FS-522, MicroLab's top of the line laboratory interface. The PC windows below show the graphical rendering spectra one obtains on a series of green food coloring  samples using the FAST-spec spectrometer. The software also displays computed "visual spectra" of the blank and sample to relate the graphical absorbance spectrum to what one would see visually through the Visual Spectrometer or a diffraction grating. The Beer's Law plot's wavelengths can be changed instantly by clicking on the color bar in spectrum. The spectrum of any one sample can be displayed by clicking on the Beer's Law point.