Diffraction Grating Spectrometer and light sources.
1. The spectrometer. These are simple cardboard or plastic devices. Light enters through a narrow slit. You view through an eyepiece which is made of diffraction grating material. This disperses light much more effectively than a glass prism. As you view through the eyepiece you will see the slit over toward one side. That slit is where light enters the spectrometer. The slit must be aimed at light sources.
Light then disperses at the grating and enters your eye.
DO NOT AIM AT THE SUN.
2 Once you view the slit, and play looking at some spectra, you should look up at any overhead fluorescent light source and you will see a spectra. You may see several different “rainbow “ bands of color. The eyepiece grating can be rotated slightly to alter the view. The spectra should be lined up with the film reading scale in the spectrometer. We will use the nanometer scale to read off wavelengths.
If needed (depending on the spectrometer) You should adjust the film reading scale so that the spectra overlaps with the nm scale, but also so that the green line in mercury (overhead lights) is at approximately 546nm. You may need to periodically recheck this.
3. You are now ready to examine several sources of light. You should Identify each as either continuous, emission, or absorption spectra. If you are not sure which then write down what you think, discuss and explain what you see. For each of the sources identify the type of spectra, for emission sources make sure you measure wavelengths for prominent (most intense) spectral lines.
4. Use several sources indicated and characterize these (type and wavelengths if appropriate). Give your results for any emission sources and or absorption sources--- give wavelengths and post on the board in lab. Sources to look at:
Sodium:
Mercury discharge lamp
white light (incandescent light bulbs)
The sky (NOT THE SUN):
At least one other spectral discharge lamp in lab
5. Other sources. Go out and look for other sources of light. There are many around the building and also in the classroom.
When you look for these other sources (identify the source), try to predict what type of spectra will be produced before you look through the spectrometer. Discuss your prediction, and then go ahead and take a look. Record your results.
Source 1) ______
Prediction discussion
Observations:
Source 2) ______
Prediction discussion:
Observations:
Source 3) ______
Prediction discussion
Observations: