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Unformatted text preview: brown (twb493) ch24-h2 chiu (56565) 1 This print-out should have 19 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A proton is briefly accelerated in the y di- rection, as shown in the figure below. + A D C B vectora At which location(s) AD will electromag- netic radiation be detected a short time later? List all that apply, separated by commas. If none apply, enter none. Correct answer: A, B, C. Explanation: The radiative electric field is non-zero at locations A, B, and C. The radiative electric field along the axis of the acceleration (point D) is zero. 002 10.0 points A proton is accelerated in the direction shown by the arrow labeled vectora in the figure below. vectorr vectora IV I VI V II III Which of the arrows labeled I-VI shows the direction of the vector vectora at the observation location indicated by the vector vectorr ? 1. II 2. V 3. VI correct 4. I 5. III 6. IV Explanation: VI is the correct choice. 003 (part 1 of 3) 10.0 points A proton located at the origin is accelerated in the y direction for a brief time. How much time passes before a detector located at ( . 9 m , , ) detects a radiative electric field? Use c = 3 10 8 m / s. Correct answer: 3 10- 9 s. Explanation: The wave propagates at the speed of light. So c = distance t t = distance c = . 9 m 3 10 8 m / s = 3 10- 9 s . 004 (part 2 of 3) 10.0 points What is the direction of the radiative electric field observed at this location? Choose the unit vector corresponding to this direction. 1. ( 1 , , ) 2. ( 1 , , ) 3. ( , 1 , ) 4. ( , 1 , ) correct 5. ( , , 1 ) 6. ( , , 1 ) brown (twb493) ch24-h2 chiu (56565) 2 Explanation: For a proton, the radiative electric field is opposite vectora , which is in the y direction. Thus, at the given location, vextendsingle vextendsingle vextendsingle vector E vextendsingle vextendsingle vextendsingle rad is in the + y direction. 005 (part 3 of 3) 10.0 points If the accelerated particle had been an elec- tron instead of a proton, what would have been the direction of the radiative electric field at this location? Choose the unit vector corresponding to this direction. 1. ( 1 , , ) 2. ( , 1 , ) 3. ( 1 , , ) 4. ( , , 1 ) 5. ( , 1 , ) correct 6. ( , , 1 ) Explanation: For an electron, the radiative electric field is in the same direction as vectora . Thus, at the given location, vextendsingle vextendsingle vextendsingle vector E vextendsingle vextendsingle vextendsingle rad is in the y direction. 006 10.0 points An electric field acts on an electron, resulting in an acceleration of 1 . 6 10 17 m / s 2 for a short time. What is the magnitude of the radiative electric field observed at a location a distance of 6 cm away along a perpendicular to the direction of the acceleration? Use the following constants: c = 3 10 8 e = 1 . 6 10- 19 k = 1 4...
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- Fall '08