Identifying Lines in the Solar Spectrum: Worksheet

Table 2 -- Determining the Scale Factor
LinesLocation of
first line
Location of
second line
Distance (pixels)Distance (nm)Scale Factor
K - F XXXXX XXXXX XXXXX 92.7 0.45
H - E
F - C
K - D2
Average: ____ nm/pixel

Table 3 -- Identification of "Unknown" Lines
Line ID (#)Distance from ref. line (pixels)Distance (nm)Calculated Wavelength (nm)Element Name
1*39 17.55410.95Hydrogen
1
2
3
4
5
6
7
8
9
10
11
12
13
*Note: This calculation assumes the K line as a reference, and assume a scaling factor of 0.45 nm/pixel. Your actual numbers may differ. You should use your numbers.

1. What does the "line width" tell you about the "strength" of the line? Is a line having a width of 1.5467 nm more evident than a line having a line width of 0.0083 nm? The strength of a line in a stellar spectrum depends upon the temperature of the star as well as the abundance of the element in the atmosphere of the star, and the ease with which electrons can move between levels in a particular atom.

2. Did you have discrepancies between your calculated wavelengths and those given in the table of wavelengths? Describe.

3. If so, why do you think this happened? In answering this question, consider your accuracy in determining the scaling factor and measuring the distance to each "unknown" line. How much of an effect did these errors have on the calculated wavelengths?

4. Suggest a better method that students might use to extract more accurate wavelengths and line identifications.

5. How do astronomers use similar processes to identify absorption lines in other stars?