LAB 13

Physics Lab 13, Tuesday, June 29, 2010 Name _____________
Dr Dave Menke, Instructor

I. Title: Spectroscopy

II. Purpose: to observe the dispersion of light and both bright and dark lines. Each spectroscope is a cylindrical tube, with a slit in one end and a circular diffraction grating at the other end.

III. Equipment: Diffraction Gratings, and/or Student spectroscopes; light sources (incandescent and gas)

IV. Procedure:
1. Take a diffraction grating (and later, a spectroscope) and point it at various light sources
2. Identify each light source used [incandescent light, gas discharge tube – Hg, He, H, Ne, or other element(s)], Sun
3. Observe and record observations. Remember that you must point the end with the slit towards the light source so that the slit is horizontal (left and right, NOT up and down). Look through the diffraction grating end, and notice to the left and to the right of the lighted slit there will be either a “rainbow” of colors, or individual bright lines.
4. Repeat 1 – 3 with a spectroscope

V. Data, observations, calculations:

A. With Diffraction Slide


Observation # Source of Light Observation
1 Light bulb
2 Sun
3 Hydrogen tube
4 Helium
5 Hg (Mercury)
6 Ne
7 Argon
(Expand your table if there are additional light sources available.

B. With Spectroscope


Observation # Source of Light Observation
1 Light bulb
2 Sun
3 Hydrogen tube
4 Helium
5 Hg (Mercury)
6 Ne
7 Argon


(Expand your table if there are additional light sources available.)

VI. Results: (This section is the same as “Conclusions,” so draw your conclusions. Start with reviewing section II Purpose, and determine if you achieved your purpose and at what level of success, e.g., complete failure to phenomenal success, and explain your level)

VII.Error Analysis

A. Quantitative: NA
B. Qualitative:
1. Personal – What did you, or your partner(s) do to screw up?
2. Systematic – What part of the environment screwed things up, e.g., weather, equipment, etc.
3. Random – As this is an observational experiment without doing multiple trials and taking averages, there is random error. We don’t know what it is, thus, we call it “random.”

VIII. Questions:
A. What is a continuous spectrum, and what causes it?
B. What is a bright line spectrum?
C. What is a dark line spectrum?
D. What kind of spectrum does the Sun have, and why?