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Graphing Spectra - A Student Worksheet

Part II.

The following spectrum represents the energy state of the element, carbon. Carbon's emission lines in the visible range are a function of wavelength from 4,000 to 7,000 angstroms. You are going to create a graphical representation of carbon's spectrum from the photographic representation. Refer to the example above to help. At the particular wavelengths, illustrate the varying brightness of carbon's emission lines. Notice that in the photographic representation of the spectrum there is an underlying continuum of emission, in addition to the bright spectral lines. This continuum is due to contamination of the spectrum by ambient light, such as small amounts of white light that are picked up by the spectrometer. Your graphical representation should include this low level of emission at all wavelengths as well as carbon's spectral line features.

carbon's spectral lines

Below you are given spectra for both hydrogen and helium. For each element, select two of the brightest emission lines at the particular wavelengths and measure the wavelengths. The scale of the spectrum is indicated by the ruler below. Solve for the frequency and energy of these lines, using the relationships between wavelength and requency and between frequency and energy. (Hint: You will have to manipulate an equation.) After the flame test, you will complete the same calculations for the following elements: sodium and calcium.

spectrum of Hydrogen and Helium, with a scale

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