Announcement Test 2 is coming up on Mar 19. Start preparing! This test will cover the classes from Feb 27 - Mar 14. 50 points, scantron, 1 hr. 1
AST 103 Light, Atoms, and Spectra (continued) Analyzing Spectra Prof. Ken Nagamine UNLV 2
Quiz Use the graph to determine which of the following best describes how Star A would appear as compared with Star B? a) Star A would appear more red than Star B. Star A visible range b) Both stars would appear more red than blue. c) Both stars would appear more blue than red. d) Star A would appear more blue than Star B. e) None of the above. Energy Output per second Star B V I B G Y O R Wavelength 3
Quiz Use the graph to determine which of the two stars (A or C) is at a higher temperature? a) Star A b) Star C c) The two stars have the same temperature. d) It is not possible to infer this relationship. Energy Output per second visible range Star A 8000" Star C V I B G Y O R Wavelength 4
What physical situation makes this spectrum? 5
Hot/Dense Energy Source prism Cooler low density cloud of Gas Absorption Line Spectrum 6
The Sun s Spectrum A hot dense core surrounded by a low density outer atmosphere 7
All stars produce absorption spectra 8
Quiz Imagine that you observe the Sun using a telescope in an orbit high above Earth s atmosphere. Which of the following spectra would you observe by analyzing the sunlight? A. absorption spectrum B. emission spectrum C. continuous spectrum D. none of the above 9
Energy Level Transitions The only allowed changes in energy are those corresponding to a transition between energy levels Not Allowed Allowed 10
Chemical Fingerprints Downward transitions produce a unique pattern of emission lines 11
Chemical Fingerprints Each type of atom has a unique spectral fingerprint Observing the fingerprints in a spectrum tells us which kinds of atoms are present 12
LecturTutorial (LT): Light and Atoms (pp. 63-67) Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group. If you get really stuck or don t understand what the LT is asking, ask for help. 13
LT: Light and Atoms #4 - student debate A B 14
Quiz Which of these would cause a highest energy absorption line? A B C D E. None of the above (show white side of card) 15
Quiz Which of these shows the atom emitting the highest energy photon? A B C D E (E. show white side of card) 16
Quiz Which of these shows the atom absorbing the highest energy photon? A B C D E (E. show white side of card) 17
Quiz Which of these shows the atom emitting the lowest energy photon? A B C D E (E. show white side of card) 18
What can we learn by analyzing starlight? A star s temperature A star s chemical composition 19
LecturTutorial (LT): Analyzing Spectra (pp. 69-72) Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group. If you get really stuck or don t understand what the LT is asking, ask for help. 20
Consider the absorption spectra shown below for Star X and Star Z. What can you determine about the color of the two stars? Assume that the left end of each spectrum corresponds to shorter wavelengths (blue light) and that the right end of each spectrum corresponds with longer wavelengths (red light). Star X Star Z A. Star X would appear blue and Star Z would appear red. B. Star X would appear red and Star Z would appear blue. C. Both stars would appear the same color. D. The color of the stars cannot be determined from this information. 21