Summer Research Program for Secondary School Science Teachers

David Deutsch

Manhattan Center for Science and Mathematics

Summer 2000

Verifying the Energy Levels for a Hydrogen Atom Listed in the New York State Physics Regents Tables

Aim/Problem : Can we verify the energy levels for a hydrogen atom listed in the New York State Physics Regents tables?  (table from a standard physics textbook could be substituted)

Objectives: The student will be able to

1.       Use the given equipment to view the spectral lines of hydrogen.

2.       Determine an appropriate procedure for determining the wavelengths of those lines. [Content Standard A- Design and conduct scientific investigations]

3.       Use Planck’s Law to determine the energy for each spectral line.

4.       Compare measured energies to the reference table and account for any discrepancies.

Materials:              Hydrogen gas tube                                                      Meter Stick

High Voltage Source                                                   Protractor

Diffraction Grating (known slit width)                           Reference Tables

Optical Stands (for gratings) [Teaching Standard D- Make materials accessible]

Plan:              1.   The teacher will demonstrate proper handling of equipment.  In particular,

safe handling of the glass tubes and high voltage sources will be demonstrated.

The teacher should also discuss possible smudging of diffraction gratings. [Teaching Standard D - Ensure a safe working environment]

2.      Student groups will meet (briefly) to establish procedures for solving the problem.  Note that steps 1 and 2 could occur in class the day before a lab period. [Teaching Standard B - Orchestrate scientific discourse]

3.      The teacher will monitor student progress in solving the problem.  In the event that a group becomes stuck, the teacher can ask a series of leading questions to encourage groups toward a sensible procedure.  In the approximate order that they may be relevant, some such questions are: [Teaching Standard B- Focus and support inquiries]

·         Have you found the slit-to-screen distance (L)?

·         Why were you told the distance between the slits (d) on the diffraction grating?

·         What colors have you found in the spectrum of hydrogen?

·         How will you determine the distance of each spectral line from the central pattern (x)?

·         How will you determine the wavelength of each spectral color? (Ans: Use Young’s Double Slit Formula,  (wavelength/x) = (d/L)) [Content Standard Unifying Concepts- Change, constancy, and measurement]

·         How will you present your data in your report?

·         Why can each wavelength of light be associated with the energy of a photon? [Content Standard Unifying Concepts- Systems, order, and organization] [Content Standard B- Matter/Energy interactions]

·         How will you determine the energy of each photon? (Ans: Planck’s Law, E = hf)

·         How can you convert wavelengths into frequencies? (Ans: c = f*wavelength)

·         Are your energy units comparable to those on the reference tables?

·         How will you convert from joules to eV ?

·         How can you use the reference tables to calculate photon energies?

·         How do the energies you measured compare to those obtained from the reference tables?

·         Which energy level transitions did you observe?

·         Have you observed all of the colors predicted by the table?  Why or why not?  (Ans:  some photons are not in the visible part of the spectrum) [Content Standard B- Structure of atoms]

4.      As a post-lab exercise, student groups can be encouraged to share results,

looking for, among other things, novel approaches to data collection, class

averaging, and suggestions for improvement to the lab.

5.      Students complete a report following the conventions outlined on the student

sheet.  The report should detail the chosen method (procedure), present the data,

and describe the solution to the problem ( did the reference table predict the

colors in the spectrum of hydrogen? ).  The discussion section challenges the

student to infer the results of spectral analysis on light from different gases and

what the importance may be to astronomers.

6.      A future lesson will review actual spectroscopy of stellar objects.

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### Name: _______________________________Date: ________________

Regents Physics – Laboratory – Spectral Analysis

Problem:  Can we verify the energy levels for a hydrogen atom listed in the New York State Physics Regents tables?

Materials:              Hydrogen gas tube                                                      Meter Stick

High Voltage Source                                                   Protractor

Diffraction Grating (known slit width)                           Reference Tables

Optical Stands (for gratings)

Grading Rubric:

Your report will be graded according to the following criteria:

1.       Does your report follow the rules of standard written English? (10 points)

2.       Is your report neat and easy to read? (5 points)

3.       Have you clearly detailed the method or procedure you have used to solve the problem? (10 points)

4.       Have you included appropriate data tables?  Are all of your measurements recorded? (15 points)

5.       Have you clearly explained and shown any calculations you needed to make? (15 points)

6.       Based on your data, have you drawn a conclusion? (15 points)

7.       Have you included a DISCUSSION section in which you fully address at least these three questions:

a.       What would the effect be if you had used a gas tube with an element other

than hydrogen in it? (15 points)

b.       Why do you think spectral analysis is important to astronomers who observe

starlight? (10 points)

c.        Can you suggest any improvements to this lab? (5 points) [Teaching Standard D- Engage students in designing the learning environment]

Due Date:

This lab is due at the beginning of class on ______________________________________

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