class21 - Announcements: Reading for Wednesday: 11.9 &...

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: Exam 2 is next week (Tue. March 9 th , 7:30- 9:15pm) Topics: TZD, Chapters 1-5, 11.9, 11.10 Practice exam is posted on CUlearn. (Disclaimer: The exam next week will not be the same as the one posted.) Summary of important Ideas Hydrogen Lithium 1) Electrons in atoms are found at specific energy levels 2) Different set of energy levels for different atoms 3) one photon emitted per electron jump down between energy levels. Photon color determined by energy difference. 4) If electron not bound to an atom: Can have any energy. (For instance free electrons in the PE effect.) Energy Electron energy levels in 2 different atoms: Levels have different spacing (explains unique colors for each type of atom. Atoms with more than one electron … lower levels filled. (not to scale) The Rydberg formula describes a. the colors of light emitted from all types of atoms. b. the angular distribution of particles scattering off Quiz on the reading Q1 b. the angular distribution of particles scattering off of atoms that Rutherford observed in his famous experiment. c. the colors of light emitted by hydrogen atoms. d. the energy distribution of cathode rays e. the frequencies of light emitted by helium atoms. Now we know about the energy levels in atoms. But how can we calculate/predict them? Need a mode Step 1: Make precise, quantitative observations! Step 3: Put your model to the test. Need a model Balmer series: A closer look at the spectrum of hydrogen 656.3 nm 486.1 434.0 410.3 Balmer (1885) noticed wavelengths followed a progression As n gets larger, what happens to wavelengths of emitted light? λ gets smaller and smaller, but it approaches a limit. 2 2 1 2 1 nm 19 . 91 n - = λ where n = 3,4,5, 6, …. Balmer series: A closer look at the spectrum of hydrogen 656.3 nm 486.1 410.3 Balmer (1885) noticed wavelengths followed a progression 434.0 2 2 1 2 1 nm 19 . 91 n - = where n = 3,4,5,6, …. λ gets smaller and smaller, but it approaches a limit gets smaller as n increase gets larger as n increase, but no larger than 1/4 364.7nm nm 19 . 91 * 4 limit = = Balmer correctly predicted yet undiscovered spectral lines. So this gets smaller
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This note was uploaded on 08/24/2010 for the course PHYS 2130 taught by Professor Staff during the Spring '08 term at Colorado.

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class21 - Announcements: Reading for Wednesday: 11.9 &...

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