Color and Spectra

Purpose: To visualize the quatization of emery levels by viewing emitted photon wavelengths and to use spectroscopy to identify an unknown gas.

Equipment:

• 2 meter sticks (one 2m and the other 1m)
• Stands
• A Diffraction Grading
• Incandescent lamp
• Hydrogen Tube
• florescent tube
• Misc Tube

Procedure: Place the 2-meter meters stick on a flat surface and place a diffraction grading at one end and an Incandescent lamp at the other. Perpendicular to this stick and close to the lamp place the other meter stick. Since we are using high voltage we must take the appropriate precautions. We place the florescent tube in the lamp being careful to only use one hand.
      We turn on the lamp and dim the other lights. By looking through the diffraction grating at the tube you should notice a rainbow of colors. With a partners help to identify the location on the second meter stick locate the edges of this spectrum and identify the middle of red, blue and the green color regions.
     We observed a violet to red spectrum with violet being closest to the bulb. The wavelengths recorded were:

violet edge	36.7	±	0.5	m
blue	45.5	±	0.5	m
green	53.7	±	0.5	m
red	70.3	±	0.5	m
red edge	83.5	±	0.5	m

Using the ideas of constructive interference through a double slit we derive the following:

Values for our experiment:
     L=1.96  0.003m
     d=0.0020 mm

Then using the edge of the spectra we are examining and the accepted span of the visible spectra we can create an equation to correct any errors with our set up. To do this we calculate the wavelengths of the edge of the spectra (the lowest violet and furthest red) and then set up the following system of equations and solve.

Having this equation allowed us to correct any errors in future wavelengths.

   

 For the next part, to test our calculation and the theoretical values of hydrogen spectrum, we examined the spectrum lines for hydrogen.
We set up a lamp that is high voltage and place a hydrogen tube in it with the same set up and practice as before (using two partners to determine where the spectrum lines are and plugging them into the wavelength equation and the correction equation) we calculate the wavelengths. We also include the percent error.

 For the final part of this project we take a look at the application of the process of spectroscopy: Identifying an unknown. We were given an unknown gas and were asked to identify it. The gas in plasma state is shown below and the same procedures were used as in the hydrogen spectra to identify the wavelengths of the spectra.

We observed very faint lines in the red violet and cyan color regions. The black shows the wavelengths and their uncertainties.

Using the internet to look up spectrum lines, we discovered that our unknown was XE.

Conclusion: Spectrometery is a very simple but very useful tool and we were able to use it to not only identify an unknown but verify very important aspects of quantum mechanics.