Introduction
A spectrometer is a device that utilizes a light-dispersing element, known as a diffraction grating, to split a light source into its component colors. In this way characteristic emission spectra can be observed to aid in identifying what species is emitting.

The Spectrometer
We will use the blue spectrometers, which were assembled by the manufacturer (in past years we've built spectrometers from a kit). You view the spectra through the disk eyepiece, which is a diffraction grating. This has finely-ruled lines on it that cause light to be deflected by an angle that is proportional to the light wavelength, thus separating the wavelengths in space. Your eye images the incoming light and it appears to come from a source that is at some angle with respect to the path of the incoming light through the slit. In this way, you see different colored images of the source, which appear against the film scale of the spectrometer, to the left of the slit where the light enters.

Observations
1. Calibration - As a check on the accuracy of your spectrometer, observe the mercury lamp, which appears to be a bright blue to the unaided eye. You should see the following spectral lines:

Yellow - 577, 579 nm Green - 546 nm Blue - 436 nm

Record your observed wavelengths here and comment:

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Note that you can move the spectrometer left and right so that the slit sweeps by the source, and the spectral lines appear to move on the film, creating uncertainty in the actual wavelengths. It's probably best to assume that the correct wavelength is obtained in roughly the middle of this range of adjustment. The intensity of the lines should be greatest here as well. If the observed wavelengths differ slightly from those above, you can use these differences to adjust subsequent measurements. For example, if you see the green line at 545 nm, your spectrometer reads 1 nm too low, so if you observe another spectral line at 531 nm, you can assume that this line is actually closer to 532 nm.

2. Other lamps - Observe the spectra of the other three lamps, which are numbered and placed around the room. Record their wavelengths here, keeping track of the lamp number.

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Use the table below of some observed spectral lines to identify each lamp.

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3. Fluorescent lights - Holding the spectrometer up to an overhead fluorescent lamp such that the light tube is parallel to the entrance slit, observe the spectrum of the lamp. Describe it below. Do any spectral lines stand out, and if so, can you identify which element is present within the tube?

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4. Solar spectrum - The sun is approximately a blackbody, so you would expect to see a continuous visible spectrum if you view sunlight through the spectrometer. Look towards (but not directly at!) the sun with your spectrometer and observe the spectrum. Is it different than you might have expected, and if so, what features do you observe that are unexpected? If you see "spectral lines," note some of their wavelengths. Any idea where these come from??

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5. Question: What causes there to be "characteristic emission wavelengths" for each spectral lamp?

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