Printed: Apr/20/2009 Activity: Spectra Page IA- 1 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/aturedvendorproduct.aspx?uid=72438 o Some good pictures of spectra through this scope: http://home.comcast.net/%7emcculloch-brown/astro/spectrostar.html
Page IA- 2 Spectra Printed Apr/20/2009 I. Introduction (in class) Table of Contents 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!
Printed: Apr/20/2009 Activity: Spectra Page IA- 3 A. Black Body Radiation II. Theory (more given in lecture) 1b. Josef Stefan s Law 1879 31 Experimentally shows total output of light of a hot dense (black) body is proportional to 4 th power of the temperature (in Kelvin) Power (watts)=aσt 4 σ=5.67x10-8 Watts/(m 2 -K 4 ) A=surface area 1884 Ludwig Boltzmann (former student of Stefan) derives formula from thermodynamics. I was a guest speaker (Sept 2005) at the Josef Stefan Institute in Slovenia. 2a. Wien s Displacement Law 33 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
Page IA- 4 Spectra Printed Apr/20/2009 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 spectrum 2. A hot transparent gas will emit emission line spectrum 3. A cool transparent gas in front of a source of continuous spectrum will produce absorption spectra. 2a. Kirchhoff s Laws 49
Printed: Apr/20/2009 Activity: Spectra Page IA- 5 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 n 1 =2, n 2 ={3,4,5} 1895 Paschan Series discovered in IR, described by n 1 =3 1908 Lyman Series discovered in UV, described by n 1 =1 3g. Spectral Series 58
Page IA- 6 Spectra Printed Apr/20/2009 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]
Printed: Apr/20/2009 Activity: Spectra Page IA- 7 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.
Page IA- 8 Spectra Printed Apr/20/2009 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?
Printed: Apr/20/2009 Activity: Spectra Page IA- 9 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?
Page IA- 10 Spectra Printed Apr/20/2009 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=
Printed: Apr/20/2009 Activity: Spectra Page IA- 11 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=
Page IA- 12 Spectra Printed Apr/20/2009 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!
Printed: Apr/20/2009 Activity: Spectra Page IA- 13 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.
Page IA- 14 Spectra Printed Apr/20/2009 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, sharply qefined on side towards violet, due to terrestrial oxygen. a B C 1,2 E2 El b1 b2 b3 b4? 6867 6563 Red Red Red H2O O2 H 5896,5890 Orange-Yellow Na 5270 5183 5184 5173 5168 5167 Green Green Green Green Green Green Ca Mg Mg Mg Narrow Band, Terrestrial Water Vapor. Band similar to A, Terrestrial Oxygen Balmer H Line (solar). C1 Double Balmer Sodium Line (solar). Close group of lines and Calcium (solar) Close group of lines Magnesium and Iron due to Iron, due to Solar F 4861 Blue-Violet H G 9 h H K L M N 0 p Q R G1 G1 G2 51 2 5 ' T t U 4340 4307.7 4307.9 4227 4102 3968 3934 3820 3727 3581 3441 3361 3287 3179,3181 3100 3048 3021 2994 2948 Violet Violet Violet Violet Extreme Violet Extreme Violet Extreme Violet Extreme Violet H Ca Ca H Ca Ca Ti Ca Balmer H~ Line (solar). Composite Band, include solar: Balmer Hy Line Calcium Iron Calcium Balmer Hn Line (solar). Very Brodd Very Broad (Not seen by Fraunhofer). Titanium Double Calcium line 0 Triple Line, spacing 0.4 A 50-7 IS-:;Z- ~
205 TABLE SO-II ELEMENTS AND SOLAR ABUNDANCES. Atomic Number Symbol Name Atomica Welght Solar Abundanceb (Relative to Hydrogen=1012) 1 2 3 4 5 H He Li Be B hydrogen helium lithium beryllium boron ;1..01 4.00 6.94 9.()1 10.81 1012 6.3 x 1010 10 X 101 1.4 X 101 1.3 X 102 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 C N 0 F Ne Na Mg Al Si P S Cl Ar K Ca carbon nitrogen oxygen fluorine neon sodium, magnesium aluminum silic,on phosphorus sulphur chlorine argon potassium calcium 12.01 14.01 16.00 19.00 20.18 2~.99 24.31 26.98 28.09 30.97 32.06 35.45 39.95 3,9.10 40.08 4.2 X 108 8.7 X 107 6.9 X 108 3.6 x 104 3.7 X 107 1.9 X 106 4.0 X 107 3.3 X 106 4.5 X 107 3.2 X 105 1.6 X 107 3.2 X 105 1.0 X 106 1.4 X 105 2.2 X 106 21 22 23 24 25 26 27 28 29 30 Sc Ti V Cr Mn Co Ni Cu Zn scandium titanium vanadium chromium manganese.iron cobalt nickel copper zinc 44.96 47.90 510.94 52.00 54.94 55.85 58.93 58.71 6,3.55 65.37 1.1 X 103 1.1 x 105 1.0 X 104 5.1 X 105 2.6 X 105 3.2 X 107 7.9 X 104 1.9 X 106 1.1 X 104 2.8 X 104 31 32 33 34 35 Ga Ge As Se Br gallium germanium arsenic selenium bromine 69.72 12.59 14.92 18.96 79.90 6.3 X 102 3.2 X 103 36 37 38 39 40 Kr Rb Sr y Zr krypton rubidium strorjtium yttrium zirconium 83.80 85.47 87.62 88.91 91.22 4.0 X 102 7.9 X 102 1.3 x 102 5.6 X 102 50-8
206 Atomic Number Symbol.Name Atomica Weight Solar AbundanceJ (Relative to Hydrogen=lO12) 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er 1m Yb Lu Hf Ta W Re niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon caesium barium lanthanum cerium praseodymium neodymium prome!thi urn samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium 1 ute1: i urn hafnii urn tantalum tung~;ten rhenium 92.91 95.94 98.91 1011.07102.91 106.4 107.87 11'2. 40 114.82 118.69 1211.75 127.60 126.90 131.30 132.91 137.34 138.91 140.12 140.91 144.24 146 150.4 151.96 157.25 158.93 162.50 164.93 167.26 1Q8.93 110.04 174.97 178.49 180.95 183.85 1$6.2 7.9 X 101 1.4 X 102 6.8 X 101 2.5 X 101 3.2 X 101 7.1 7.1 x 101 4.5 X 101 1.0 X 102 1.0 X 101 <7.9 X 101 1.2 X 102 1.3 x 101 3.5 X 101 4.6 1.7 x 101 5.2 5.0 1.3 x 101 1.1 X 101 5.8 1.8 7.9 5.8 6.3 5.0 X 101 <0.5 76 77 78 79 80 81 82 83 84 85 as Ir pt Au Hg T1 Pb Bi Po At osmi IJm iridium p 1 at'i num gold mercury thallium lead bismuth polonium astatine 190.2 192.2 195.09 196.97 200.59 204.37 207.19 208.98 2110 2'10 5.0 7.1 5.6 x 101 5.6 <1.3 x 102 7.9 8.5 x 101 <7.9 X 101 50-9 tf1
.:. 207 Atomic Number Symbol Name Atomica Weight Solar Abundance (Relative to Hydrogen=1012) 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Ha radon 222 francium 223 radi IJm 226.03 actinium 227 thorium 232.04 protactinium 230.04 uranium 238.03 neptljni urn 237.05 plutonium 242 americium 242 curium 245 berkt~ 1 i urn 248 californium 252 ei ns.tei ni urn 253 fermium 257 mendelevium 257 nobelium 255 lawrencium 256 rutherfordium 261 hahnium 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 been observed on the sun. I~b ~ 50-10