Printed: Apr/20/2009 Activity: Spectra Page IA- 1
©2009 W. Pezzaglia Astronomy Lab Manual Updated:2009Apr20
NAME_______________ NAME__________________ __________________ NAME_______________ NAME__________________ __________________
Spectra
Project Star Spectroscope (Learning Technologies)
Equipment:
• Plastic Spectroscopes (Learning Technologies, Project STAR) • Vernier Spectroscopes (with grating or prism for detailed measurements) • Color Filter Set (red, yellow, green, blue, violet, interference) • Red Laser • Spectra Tubes
o Known spectra:Hydrogen, Helium, Sodium, Mercury, Neon, and others o Some unknown sources
• Fluorescent light • Incandescent Light with variable power supply
References o Spectra Demo: http://jersey.uoregon.edu/elements/Elements.html o Spectroscopes:
http://www.sciproj.com/FeaturedVendorProduct.aspx?uid=72438 o Some good pictures of spectra through this scope:
http://home.comcast.net/%7emcculloch-brown/astro/spectrostar.html
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Table of Contents I. Introduction (in class) II. Theory (very rough notes)
A. Black Body Radiation (Stefan and Wien Law) B. Spectra Types (Kirchhoff’s Laws) C. Atomic Spectra
III. Lab Activities
Part A White Light 1. White Light at full power 2. Change in Temperature 3. Filtered White Light
Part B: Spectra Observation 1. Known Spectra 2. Fluorescent Light 3. Unknown Spectra 4. Data Sheet #1 (Known Spectra) 5. Data Sheet #2 (Unknown Spectra)
Part C: Laser Light 1. Predictions 2. Experiment 3. Conclusion
Part D: Fraunhofer Spectra 1. Observation 2. Table of Fraunhofer Lines 3. Table of Solar Abundances
Its possible not all of the above will be assigned. Be sure to read the assignment as given on the board!
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©2009 W. Pezzaglia Astronomy Lab Manual Updated:2009Apr20
II. Theory (more given in lecture) A. Black Body Radiation
1b. Josef Stefan’s Law 1879• Experimentally shows total output of
light of a hot dense (black) body is proportional to 4th power of the temperature (in Kelvin)
• Power (watts)=AσT4
• σ=5.67x10-8 Watts/(m2-K4)• A=surface area
• 1884 Ludwig Boltzmann (formerstudent of Stefan) derives formulafrom thermodynamics.
• I was a guest speaker (Sept 2005) at theJosef Stefan Institute in Slovenia.
31
2a. Wien’s Displacement Law• 1893 shows that the “color” of black
body is inversely proportional to temperature.
• λ = α/T• Wien’s constant
α= 2,898,000 nm-K• So T=6000ºK gives
λ=483 nm
33
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©2009 W. Pezzaglia Astronomy Lab Manual Updated:2009Apr20
B. Types of Spectra: Kirchhoff’s Laws
2b. Gustav R Kirchhoff (1860)50
His three laws:1. A hot dense body will emit a
continuous spectrum2. A hot transparent gas will emit
emission line spectrum3. A cool transparent gas in front of a
source of continuous spectrum will produce absorption spectra.
2a. Kirchhoff’s Laws 49
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C. Atomic Spectra (Bohr’s Model of Atom)
3a. Rydberg Formula 33
• 1885 Balmer comes up with formula that explains the Hydrogen lines (“Balmer Series”)
• 1888 Rydberg improves formula, where n1=2, n2={3,4,5}
•1895 Paschan Series discovered in IR, described by n1=3•1908 Lyman Series discovered in UV, described by n1=1
3g. Spectral Series 58
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III. Lab Activities Part A: White Light 1. White Light Observation (full power)
• View spectra of white light under full power (120 volts)
• For each “color” determine the “center” wavelength (in nm)
• Next estimate the start/end borders between the colors (e.g. the end of green should be the start of yellow)
• Calculate the for each color the: Width = End-Start
Color Start Center End Width Violet Indigo Blue Green Yellow Orange Red
(a) How far into the Violet (near UV) can you see before it drops off? __________ nm
(b) How far into the Red (near Infrared) can you see before it drops off?__________ nm
(c). Which “color” is the narrowest band? ___________________________
(d). Which “color” is the widest band? ___________________________
(e) Summarize: Does the white light extend as deep into the violet(red) as the most violet(red) line seen in the other spectra? [You’ll need to do part B before answering this question]
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©2009 W. Pezzaglia Astronomy Lab Manual Updated:2009Apr20
2. Change In Temperature • Lower the Power to 20% (should we change this value?)
• Notice the change in the white light spectra.
(a) Summarize: Describe the change in the spectra (quantify any change in range, and intensities of colors, e.g. does yellow drop less than blue).
(b) Center: For full power, and 20% power, estimate the “center” wavelength of the spectra. Does this center shift at all? In what direction?
(c) Interpret what you see in terms of Wien’s Law and Stephan Boltzmann law.
3. Filtered White Light (a) View white light after it has passed through colored glass filters. Summarize the filter’s effect (be
quantitative, for example, it passes 400 nm through 500 nm and blocks the rest).
(b) Interference Filter: If one is available, summarize its effect.
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Part B: Spectra (Datasheet #1 & 2) WARNING: DANGEROUSLY HIGH VOLTAGE IS APPLIED TO THE SPECTRA TUBES
There will be a number of spectra sources set up for you to observe using a hand-held spectroscope. Half of them will be “known”, the other half “unknown” for which you will try to identify the elements from the “known” sources.
Question B-1 Known Spectra (Data Sheet #1) Arc tubes will be set up (probably Hydrogen, Mercury, Neon, Sodium and Helium), most of them displaying emission spectra. For each, on Data Sheet #1:
• Label the element name • Note the “visual” color of the tube (what color it appears to your eye) • Sketch the spectra lines seen (accurately on the scale) • Classify the spectra type (Emission, Absorption, Continuous)
(a) Calibration on Hydrogen: Your spectroscope scale may not be completely accurate. The expected lines of Hydrogen are red (656 nm), blue (486 nm), indigo (434 nm) and violet (410 nm). Do you see all of these lines? Are the wavelengths you measured right on, or consistently low/high?
(b) With the naked eye, note the color of each tube. Is this color consistent with the spectral lines seen (are there any surprises, for example appears yellow, but really it only has red and green lines)?
(c) Are all the spectra of type “emission”? Are any continuous or show absorption?
(d) Do any of the tubes have a violet line which exceeds that found in white light? Do any have a red line which exceeds than found in white light?
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Question B-2 Fluorescent Light (Data Sheet #2) As your first “unknown”, view the spectra of a Fluorescent light. Sketch its spectra structure in the lower part of DataSheet#2. (a) What type of spectra structure does this display? (Emission, Continuous, Absorption)
(b) To the naked eye, a Fluorescent light appears “white”. Where does this come from (i.e. are there any “white” lines in the spectra)?
(c) Comparing the spectra to the “known” sources, can you identify which element is present in a Fluorescent light? Specifically, which lines match (give wavelengths & colors)?
Question B-3 Other Unknown Spectra (Data Sheet #2) Your lab instructor will have a number of other “unknown” sources for you to view. For each, sketch the spectra and answer the question(s) below. These sources may include (all are different)
• White Computer Screen • Red, green and blue on computer screen • Building lights, streetlights (if dark!) • Vending Machine
(a) What type of spectra structure does each display? (Emission, Continuous, Absorption)
(b) Again, consider the naked eye color, and see if you can make sense of it from the components in the spectra. Note some of these sources (n.b. the Coke Machine) may be passing through a colored glass filter (i.e. is the spectra really red, or is it white light passing through red glass)?
(c) Comparing the spectra to the “known” sources, can you identify which element is present in each of these unknowns?
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Spectra Data Sheet #1 KNOWN SPECTRA Name__________________ Element=________________ Visual Color=__________ Spectra Type=_______
Element=________________ Visual Color=__________ Spectra Type=_______
Element=________________ Visual Color=__________ Spectra Type=_______
Element=________________ Visual Color=__________ Spectra Type=_______
Element=________________ Visual Color=__________ Spectra Type=_______
Element=________________ Visual Color=__________ Spectra Type=_______
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©2009 W. Pezzaglia Astronomy Lab Manual Updated:2009Apr20
Spectra Data Sheet #2 UNKNOWN SPECTRA Name__________________ Object=Fluorescent light Visual Color=__________ Spectra Type=_______
Object=________________ Visual Color=__________ Spectra Type=_______
Object=________________ Visual Color=__________ Spectra Type=_______
Object=________________ Visual Color=__________ Spectra Type=_______
Object=________________ Visual Color=__________ Spectra Type=_______
Object=________________ Visual Color=__________ Spectra Type=_______
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©2009 W. Pezzaglia Astronomy Lab Manual Updated:2009Apr20
Part C: Laser Light 1. Prediction/hypothesis: Before doing an experiment, make a prediction!
(a) Red Filter: If you shine red laser light through a red filter what do you think will happen?
(a) Yellow Filter: How about through a Yellow Filter? Explain your reasoning!
(c) Green Filter How about through a green Filter? Explain your reasoning!
(d) Blue Filter How about through a blue Filter? Explain your reasoning!
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©2009 W. Pezzaglia Astronomy Lab Manual Updated:2009Apr20
2. Experiment: Now actually do the experiment. (a) Red Filter: What happened? Did it match your expectations?
(b) Yellow Filter: What happened? Did it match your expectations?
(c) Green Filter What happened? Did it match your expectations?!
(d) Blue Filter What happened? Did it match your expectations?
3. Conclusion: Summarize what is happening when you shine a red laser light through a filter.
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Part D: Fraunhofer Spectra Question E-1 Fraunhofer Lines WARNING: DO NOT POINT SPECTROSCOPE DIRECTLY AT THE SUN unless its setting/rising. Instead point it at blue sky or the sunlight through a tree or other obscuring device. You should be able to see many of the Fraunhofer absorption lines (the ones with Capitol letters), but not all of them (e.g. the ones with small letters).
(a) Data: Sketch all the Fraunhofer (absorption) lines seen in the scale below..
Blue Sky=________________ Visual Color=__________ Spectra Type=_______
(b) Compare your observations with the table provided. Summarize which Fraunhofer lines you could see, include their wavelengths, and compare to the values listed in the table. You probably saw some of the lines with CAPITOL letters (e.g. C and D lines), but not many of the others.
(c) Do the Fraunhofer lines that you most easily see correspond to elements which are most common in the solar system? [Refer to “Solar Abundance” table]
204
TABLE 50- PRINCIPLE FRAUNHOFER LINES
Line
Name*Wavelength
0
A (A)
Color Element Notes
A 7621,7594 Deep Red O2 Band in extreme red, sharplyqefined on side towards violet,due to terrestrial oxygen.
?68676563
aBC
RedRedRed
H2OO2H
°1,2E2
El
5896,5890 Orange-Yellow Na
Narrow Band, Terrestrial Water Vapor.Band similar to A, Terrestrial OxygenBalmer H Line (solar).
C1
Double Balmer Sodium Line (solar).
52705183
GreenGreen
FeCa
Close group of lines due to Iron,and Calcium (solar)
b1b2b3b4
5184517351685167
GreenGreenGreenGreen
MgMgFeMg
Close group of lines due to SolarMagnesium and Iron
F 4861 Blue-Violet H
G VioletVioletVioletViolet
Balmer H~ Line (solar).
Composite Band, include solar:Balmer Hy LineCalciumIron
G1
G1G2
43404307.74307.9
HCaFe
4227410239683934
Extreme VioletExtreme VioletExtreme VioletExtreme Violet
9hHK
CaHCaCa
CalciumBalmer Hn Line (solar).Very BroddVery Broad (Not seen by Fraunhofer).
3820372735813441336132873179,318131003048302129942948
LMN0pQR
51 25 '
TtU
uvuvuvuvuvuvuvuvuvuvuvuv
FeFeFeFeTiFeCaFeFeFeFeFe
Titanium
Double Calcium line 0Triple Line, spacing 0.4 A
IS-:;Z-
~50-7
205
TABLE SO-II ELEMENTS AND SOLAR ABUNDANCES.
AtomicNumber
AtomicaWelghtSymbol Name
Solar Abundanceb(Relative to Hydrogen=1012)
12345
6789
10
11121314151617181920
2122232425
2627282930
3132333435
3637383940
HHeLiBeB
CN0FNe
NaMgAlSiP
SClArKCa
ScTiVCrMn
FeCoNiCuZn
GaGeAsSeBr
KrRbSryZr
hydrogenheliumlithiumberylliumboron
carbonnitrogenoxygenfluorineneon
sodium,magnesiumaluminumsilic,onphosphorus
sulphurchlorineargonpotassiumcalcium
scandiumtitaniumvanadiumchromiummanganese
.ironcobaltnickelcopperzinc
galliumgermaniumarsenicseleniumbromine
kryptonrubidiumstrorJtiumyttriumzirconium
;1..01
4.00
6.949.()1
10.81
12.01
14.01
16.00
19.0020.18
2~.9924.3126.9828.09
30.97
32.06
35.45
39.95
3,9.1040.08
44.9647.90
510.9452.00
54.94
55.8558.93
58.716,3.5565.37
69.7212.5914.92
18.9679.90
83.8085.4787.6288.9191.22
10126.3 x 101010 X 101
1.4 X 1011.3 X 102
4.2 X 1088.7 X 1076.9 X 1083.6 x 1043.7 X 107
1.9 X 1064.0 X 1073.3 X 1064.5 X 1073.2 X 105
1.6 X 1073.2 X 1051.0 X 1061.4 X 1052.2 X 106
1.1 X 1031.1 x 1051.0 X 1045.1 X 1052.6 X 105
3.2 X 1077.9 X 1041.9 X 1061.1 X 1042.8 X 104
6.3 X 1023.2 X 103
4.0 X 1027.9 X 1021.3 x 1025.6 X 102
50-8
206
AtomicaWeight
AtomicNumber Symbol .Name
Solar AbundanceJ(Relative to Hydrogen=lO12)
4142434445
4647484950
5152535455
5657585960
6162636465
6667686970
7172737475
7677787980
8182838485
NbMoTcRuRh
PdAgCdInSn
SbTeIXeCs
BaLaCePrNd
PmSmEuGdTb
DyHoEr1mYb
LuHfTaW
Re
asIrptAuHgT1PbBiPoAt
92.9195.9498.91
1011.07102.91
106.4107.8711'2. 40114.82118.69
1211.75127.60126.90131.30132.91
137.34138.91140.12140.91144.24
146150.4151.96157.25158.93
162.50164.93167.261Q8.93110.04
174.97178.49180.95183.851$6.2
190.2192.2195.09196.97200.59
204.37207.19208.9821102'10
7.9 X 1011.4 X 102
6.8 X 1012.5 X 101
3.2 X 1017.17.1 x 1014.5 X 1011.0 X 102
1.0 X 101
niobiummolybdenumtechnetiumrutheniumrhodium
palladiumsilvercadmiumindiumtin
antimonytelluriumiodinexenoncaesium
bariumlanthanumceriumpraseodymiumneodymiumprome!thi urnsamariumeuropiumgadoliniumterbium
dysprosiumholmiumerbiumthuliumytterbium1 ute1: i urnhafnii urntantalumtung~;tenrhenium
osmi IJmiridiump 1 at'i num
goldmercurythalliumleadbismuthpoloniumastatine
<7.9 X 101
1.2 X 1021.3 x 1013.5 X 1014.61.7 x 101
5.25.01.3 x 101
1.1 X 101
5.81.87.9
5.86.3
5.0 X 101<0.5
5.07.15.6 x 1015.6
<1.3 x 102
7.98.5 x 101
<7.9 X 101
50-9
tf1
207.:.
AtomicaWeight
AtomicNumber Symbol Name
Solar Abundance(Relative to Hydrogen=1012)
8687888990919293949596979899
100101102103104105106
RnFrRaAcTh
PaUNpPuAm
CmBkCfEsFm
MdNoLrRfHa
radon 222francium 223radi IJm 226.03actinium 227thorium 232.04
protactinium 230.04uranium 238.03neptlJni urn 237.05plutonium 242americium 242
curium 245berkt~ 1 i urn 248californium 252ei ns.tei ni urn 253fermium 257
mendelevium 257nobelium 255lawrencium 256rutherfordium 261hahnium 262
(Reported 1974) 263
aAtomic weights are averages for terrestrial abundances.
bThe solar abundance for hydrogen has been arbitrarily set at 1012.
Reference: Solar abundances from John E. Ross and Lawrence H. Aller,Science, 191, 1223, 1976. Gaps indicate that the element has not beenobserved on the sun.
I~b~ 50-10
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