ATM Pre-Lab

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INCLUDE THIS SHEET AS THE FIRST PAGE OF YOUR REPORT.

Before the 1st Day of Lab


 

Student's Name: ______________________________________________________________

Partner's Name: ______________________________________________________________

 


Pre-lab Discussion Questions

  • It is your responsibility to discuss this lab with an instructor before your first day of your scheduled lab period. This signed sheet must be included as the first page of your report. Without it you will lose grade points.
  • If you find it difficult to find the proper texts and articles to refresh your memory, you may find it useful to watch some of the online videos, which are designed specifically to help you with this experiment. They are titled Energy Levels, Transitions, Light Sources and Detectors, Optical Instruments, Atomic Physics.
  • Specific information for Helium and Hydrogen can be found on the "library reprints" link. There you will find the Herzberg book, Atomic Spectra and Atomic Structure. Search through here to find energy diagrams for Hydrogen and Helium. Note: the numbers labeling the transition lines give the wavelength of the emitted photon in Angstroms. Here's the link: http://physics111.lib.berkeley.edu/Physics111/Reprints/ATM/ATM_index.htm...
    Also, this page contains the link to "Experiments in Modern Physics," by Melissinos. Read link number 45, "The Fabry-Perot Interferometer." Take your time to understand it. You will come out with a solid understanding of the instrument, as well as an understanding of its limits (resolution). 
  • You should be prepared to discuss the following before you come to lab:
  1. Draw an energy level diagram for hydrogen. Show the transitions that produce the Balmer series. What is the formula that gives the wavelengths of these lines for the simple Bohr hydrogen atom? How does the derivation of the energy levels in the Bohr model differ from the quantum mechanical methods?
  2. Write the following atomic state's abbreviation in "full spectroscopic notation" (the notation for states written in the $n, l, j, m_{j} $ basis, described in the first instructional video). This article provides a good overview of the notation, in case you need a refresher: http://www.physics.byu.edu/faculty/bergeson/physics571/notes/L27spectnot...
    A hydrogen atom in the n=3, l=2 state. Note that there are 2 possible values for J.

  3. Draw an energy level diagram for helium. Show the transitions that produce the red and yellow lines. Note the differences in the structure and splitting between the energy levels for hydrogen and helium.
  4. Draw an energy level diagram illustrating the Zeeman effect for the red line of helium. When a 1 tesla magnetic field is applied to helium, what happens to the energy levels and transitions that produce the red line of helium?
  5. What gives a spectral line a non-zero width? Estimate the line width for the first Balmer series. Assume that the pressure inside the tube is 5 torr and the temperature 600K, and that the lifetimes of the states are about 10nsec.
  6. Draw a sketch of the diffraction grating spectrometer showing the placement of the optical elements and the path and focusing of a light beam as it goes from the source through the spectrometer and to the film or photomultiplier. Explain how the grating works. Calculate a representative value for the resolving power of the grating.
  7. Is the photomultiplier output current proportional to the number of incident photons, independent of wavelength? If not, how does the output depend on wavelength?
  8. Draw a sketch of the Fabry-Perot interferometer showing the placement of the optical elements and the path of a light beam as it goes from the source through the interferometer and through the telescope. Calculate the resolving power of the interferometer. Why is it necessary to use the interferometer instead of the grating for observing the Zeeman Effect?

 

Staff Signature ______________________________________________ Date ____________

Completed on before the first day of lab? (circle)   Yes   /   No

Mid-lab Questions

On day 3 of this lab, you should have successfully produced a plot of the Balmer-series lines, and made an estimate of the Rydberg constant. Show them to an instructor and ask for a signature.

Staff Signature ______________________________________________ Date ____________

Completed by the third day of lab? (circle)   Yes   /   No

On day 5 of this lab, you should have successfully observed the Zeeman splitting of the helium lines and estimated a value for the Bohr magneton. Demonstrate this to an instructor and ask for a signature.

Staff Signature ______________________________________________ Date ____________

Completed by the fifth day of lab? (circle)   Yes   /   No


Please also fill out the Student Evaluation of Experiment.