Name: Date: PC1144 Physics IV Atomic Spectra 5 Laboratory Worksheet Part A: Mercury Spectrum Reference angular position θ 0 = Colour λ (10 7 m) θ 1 θ 2 Violet 4.047 Blue 4.358 Blue-Green 4.916 Green 5.461 Yellow 5.770 Yellow 5.790 Data Table 1 Analysis A-1: For each spectral line, calculate (1) the diffraction angle θ; and (2) the grating constant d. Determine your experimental value for the grating constant d and its corresponding uncertainty. Show a sample calculation and be sure to attach a copy of the spreadsheet to your laboratory report. Grating constant: d = ± (units) Page 1 of 5
Atomic Spectra Laboratory Worksheet Page 2 of 5 Part B: Hydrogen Spectrum Colour λ (10 7 m) n θ 1 θ 2 Violet 4.102 6 Blue 4.341 5 Blue-Green 4.861 4 Red 6.653 3 Data Table 2 Analysis B-1: For each spectral line, calculate (1) the diffraction angle θ; (2) the wavelength λ; and (3) the percentage discrepancy to compare your experimental value for wavelength with the accepted value. Show a sample calculation and be sure to attach a copy of the spreadsheet to your laboratory report. Question B-1: Comment on the accuracy of your experimental values for the wavelengths of hydrogen compared to the known values. Analysis B-2: perform a suitable linear least squares fit to your data: wavelength λ exp and n so that the Rydberg constant R H can be determined. Plot a suitable linear graph for your data. Also show on the graph the straight line that was obtained by the linear least fit to the data as well as the error-bar of your data. Be sure to attach a copy of the graph (with the spreadsheet) to your laboratory report. Independent variable x: Dependent variable y: Gradient: ± (units) y-intercept: ± (units) Correlation coefficient:
Atomic Spectra Laboratory Worksheet Page 3 of 5 Analysis B-3: Determine your experimental value for the Rydberg constant R H corresponding uncertainty. Show your work. and its Rydberg constant: R H = ± (units) Analysis B-4: Using percentage discrepancy, compare your experimental value for the Rydberg constant with the accepted value. Show your work. Rydberg constant: % discrepancy = % Question B-2: Comment on the accuracy of your experimental value for the Rydberg constant R H. Analysis B-5: Calculate the percentage discrepancy of your experimental values of the four wavelengths of hydrogen compared to the wavelengths calculated from the Balmer formula. Show your work. Violet: % discrepancy = % Blue: % discrepancy = % Blue-Green: % discrepancy = % Red: % discrepancy = %
Atomic Spectra Laboratory Worksheet Page 4 of 5 Question B-3: Using the Balmer formula, calculate the n = 7 wavelengths for the hydrogen spectrum. Why was this wavelength not observed in the laboratory? Part C: Unknown Spectrums #1 #2 #3 #4 #5 #6 #7 #8 Colour θ 1 θ 2 Data Table 3: Unknown element labeled A. Analysis C-1: For each spectral line, calculate the value of the wavelength for the visible spectrum of the unknown element labeled A. Show a sample calculation and be sure to attach a copy of the spreadsheet to your laboratory report. Question C-1: Identify the unknown element labeled A by referring to the list of wavelengths of prominent spectral lines on the website at http://hyperphysics.phy-astr.gsu.edu/hbase/quant um/atspect2.html. State clearly your basis of the choices. Unknown element A:
Atomic Spectra Laboratory Worksheet Page 5 of 5 #1 #2 #3 #4 #5 #6 #7 #8 Colour θ 1 θ 2 Data Table 4: Unknown element labeled B. Analysis C-2: For each spectral line, calculate the value of the wavelength for the visible spectrum of the unknown element labeled B. Show a sample calculation and be sure to attach a copy of the spreadsheet to your laboratory report. Question C-2: Identify the unknown element labeled B. choices. State clearly your basis of the Unknown element B: 6 Laboratory Report Submit a laboratory report within ONE week after your laboratory session. Important: Before leaving the laboratory, have a demonstrator initial on your data table(s)! Last updated: Sunday 22 nd February, 2009 11:08pm (KHCM)