GOALS

Physics

• Learn to use an optical grating to find the dominant spectral lines from a gas discharge tube.
• Try to match observed spectra from unknown gas properties.

Technique

• Try to reduce angle measurements to only one variable by picking (and finding) the "optimum" grating angle.

Errors

• Once again use the nonlinear function relations to relate angle uncertainties to errors in wavelength.
• Compare known samples to your measurements for calibration.

Question (Work out in lab book before coming to class)

1. Show that the grating relation, , implies a minimum angle for when . Can you also show that is independent of small changes in (the grating angle) when ?

References

• Weidner and Sells, 6-3, 7-3.
• Halliday and Resnick, 38-8, 38-9.
• Bueche, 32.7.