sample exam solution 1 - reyes (mr29667) Sample Exam One...

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Unformatted text preview: reyes (mr29667) Sample Exam One Shear (52375) 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. In all cases, select the answer that BEST answers the question asked. The total points on this exam is 300. Some questions provide fundamental constants in addition to those given here and on the scantron sheet. Watch your units! Shear 52375 c = 3 . 00 10 8 m/s h = 6 . 626 10 34 J s m e = 9 . 11 10 31 kg N A = 6 . 022 10 23 mol 1 E = R parenleftbigg 1 n 2 1- 1 n 2 2 parenrightbigg where R =- 2 . 178 10 18 J n ( x ) = parenleftbigg 2 L parenrightbigg 1 2 sin parenleftBig nx L parenrightBig E n = n 2 h 2 8 mL 2 n = 1 , 2 , 3 , 001 (part 1 of 2) 10.0 points When sodium is heated, a yellow spectral line whose energy is 3 . 37 10 19 J/photon is produced. What is the frequency of this light? 1. 3 . 37 10 19 Hz 2. 1 . 602 10 19 Hz 3. 5 . 09 10 34 Hz 4. 3 . 10 8 Hz 5. 3 . 37 10 11 Hz 6. 5 . 09 10 14 Hz correct 7. 5 . 9 10 7 Hz 8. none of above 9. 6 . 626 10 34 Hz Explanation: E photon = 3 . 37 10 19 J / photon = ? E photon = h = E photon h = 3 . 37 10 19 J 6 . 626 10 34 J s = 5 . 09 10 14 Hz 002 (part 2 of 2) 10.0 points What is its wavelength? 1. 3 . 10 8 m 2. none of above 3. 5 . 09 10 14 m 4. 1 . 602 10 19 m 5. 6 . 626 10 34 m 6. 5 . 9 10 7 m correct Explanation: = ? c = = c = 3 . 10 8 m/s 5 . 09 10 14 Hz = 5 . 9 10 7 m 003 10.0 points What key result from the photoelectric effect showed that classical physics did not work on the atomic scale? 1. Different metals showed different behav- iors. 2. Light intensity and electron current were related. reyes (mr29667) Sample Exam One Shear (52375) 2 3. The effect is not observed when a gas is introduced into the vacuum chamber. 4. Radiation below a certain frequency, no matter how intense, would not cause electron emission. correct 5. All metals are reflective. Explanation: When electromagnetic radiation (light) of sufficient minimum energy strikes a metal cathode, electrons are knocked off its sur- face, travel to an anode, and form a current through a circuit. Two important observations were: 1) Electrons can be ejected only if the light is sufficiently energetic. Electron ejection is independent of time or intensity. The mini- mum energy varies by element. 2) The current increases with increasing intensity and is independent of color. Therefore, light is made up of photons, each having a particular amount of energy that can be transferred to an electron during a colli- sion. If the energy is equal to or greater than the amount needed to liberate the electron, it can escape to join the photoelectric current....
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This note was uploaded on 07/24/2010 for the course CH 52375 taught by Professor Ruth during the Spring '09 term at University of Texas at Austin.

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sample exam solution 1 - reyes (mr29667) Sample Exam One...

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