Emission Spectroscopy Lab
Name:
E = hv
Date:
v=c/
h = 6.626 x 10-34J*s (Planck’s Constant)
Per:
c = 3.00 x 108 m/s (wave speed constant)
vac is the wavelength of the light emitted in vacuum
RH = 1.10 x 107 m-1(the Rydberg constant for hydrogen)
n2 and n1 (integers marking principle energy levels such that n2 > n1)
where RH is the Rydberg constant, 2.18  10_18 J, and ni and nf are the initial and
final energy levels of the electron.
I General Light Sources:
a. Observe the fluorescent light bulb in the classroom, and record the color and wavelengths of its 3 brightest
lines. Also, take this opportunity to calibrate your spectrometer.
b. Now observe an incandescent (“household”) light bulb and explain how its spectrum differs from the
fluorescent bulb’s:
c. Observe the sun’s (solar) spectra, and record the location of any shaded areas. You’ll have to look carefully!
II Identifying an Unknown Gaseous Element:
Observe the unidentified (unknown) gas discharge tube with your spectroscope. Roughly sketch what you see, labeling the
colors & wavelengths of the brightest lines or characteristic regions. We will copare this spectra to accepted spectra later
in order to identify this gaseous element.
III Gas Emission Tubes
a. Observe two of the identified gas discharge tubes AND record their general spectra below. Identify each
element, and label a couple dominant wavelengths
IV Burning Salts (fireworks)
a. Observe the burning salts AND record their general color in the table on the next page. No need to look
through a spectroscope for most of these.
Salt:
Color:
b. Look at the spectrum of one salt, and label a couple dominant wavelengths.
Post-Lab Questions:
1. Explain how line spectra can be used to identify a substance.
2. Which transition is most likely to produce a red emission line? Explain your answer:
a) n = 5  n = 2
c) n = 2n = 7
b) n = 7n = 5
d) n = 7n = 2
3. Which produces the highest frequency absorption line?
Explain your answer.
a) n = 1n = 6
c) n = 2n = 6
b) n = 3n = 4
d) n = 7n = 2
4. Calculate the energy associated with 3 of the fluorescent bulb lines. Show all calculations and units and watch
significant digits!
5. Use the Rhydberg’s constant equation to calculate the wavelength of light which would allow an electron to jump from
level 1 to level 3 in a hydrogen atom. What region of the electromagnetic spectrum would this wavelength be in?
6. Explain how the solar spectrum can be used to confirm the presence of Helium in the sun’s atmosphere.
7. Using the site:
http://jersey.uoregon.edu/vlab/elements/Elements.html, find the best spectral fingerprint match to identify the unknown
elemental gas from the emission tube that you viewed in lab. Look at the line spectrums (click on the right hand button)
(Hint: One of the first 10 elements)
8. Many of today’s energy saver bulbs contain trace amounts of mercury. How could we determine whether or not a bulb
contains mercury vapor? Observe an energy saver bulb in class and determine whether mercury seems to be present. On
what evidence did you base your answer?