Computer-generated spectra obtained using a spectrophotometer are presented on t

Question

Computer-generated spectra obtained using a spectrophotometer are presented on the pages following the Report Questions. This collection contains six spectra, labeled "A" through "F". Four of these are the spectra of elements, and the other two are those of a fluorescent light and an incandescent light bulb. The four elements are Hydrogen, Helium, Sodium, and Mercury, in order of their atomic masses. Using the emission-line wavelengths given in Reference Table 14.1, identify the spectra for He, Na, and Hg, and, by default, H. You must ignore spurious lines outside of the visible-light region, and be aware that some lines listed in the tables are very faint. Another useful hint is that fluorescent lights contain significant traces of a certain heavy-metal impurity. From the spectra, identify the corresponding elements. On the graphs of the He and Hg spectra, write in the colors of the lines. What is the trace element in the fluorescent light? Explain your reasoning.

Explanation / Answer

When working with spectra like this, it is all about comparing the expected spectrum peaks (those listed in the table) with the peaks that show up on the spectrum. The problems is that we only have three elements in the table and six spectra. The first step is to pick out the light bulb and the fluorescent light. Since both of these lights are meant to produce "whitish" light we expect a lot oflight at a bunch of wavelengths, so they must be Spectra A and B. A is the incandescent light because it has no peaks. The flouescent has a heavy metal (and therefore some peaks), so it must be Spectrum B. For the other ones we just match with the lines expected in the table. If you ar having trouble try looking for a line that only appears in one element. After making this comparison you should get the following results: E is sodium/Na, C is helium/He, F is Mecury/Hg, and D is hydrogen/H. As for labeling the colors just use the table to determine what color each of the peaks is based on their wavelength.

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