spring 2006.1 - Physics 122 Spring 2006 Section University...

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Unformatted text preview: Physics 122 Spring 2006 Section University of Maryland Department of Physics Dr. E. F. Redish Exam 2 (Make up) 4. May, 2006 Instructions: Do not open this examination until the proctor tells you to begin. 1. When the proctor tells you to begin, write your full name and section number at the top of every page. This is essential since this exam booklet will be separated for grading. Do your work for each problem on the page for that problem. You might find it convenient to either do your scratch work on the back of the page before starting to write out your answer or to continue your answer on the back. If part of your answer is on the back, be sure to check the box on the bottom of the page so the grader knows to look on the back! On all the problems except the short answer questions in problems 1.] and .2 or where it says n_ot to explain, your answers will be evaluated at least in part on how you got them. If explanations are requested, more than half the credit of the problem will be given for the explanation. LITTLE OR NO CREDIT MAY BE EARNED FOR ANSWERS THAT DO NOT SHOW HOW YOU GOT THEM. Partial credit will be granted for correct steps shown, even if the final answer is wrong. Write clearly and logically so we can understand what you are doing and can give you as much partial credit as you deserve. We cannot give credit for what you are thinking — only for what you show on your paper. All estimations should be done to the appropriate number of significant figures. At the end of the exam, write and Sign the honor pledge in the space below: “I pledge on my honor that I have not given or received any unauthorized assistance on this examination.” *** Good Luck *** NAME Physics 122 Spring 2006 1. (30 points) 1.1 A mask containing a hole in the shape of the letter L is placed between a screen and a trio of very small bulbs as shown at the right. On the diagram of the screen, sketch what you would see on the screen when the bulbs are turned on. (5 pts) 1.2 Which of the following things would happen to the pattern of light on the screen if the actions described in AB were carried out? After each action, the original situation is restored. (The changes do not cumulate.) (a) It would move up. (b) It would move down. (c) It would move to the left. (d) It would move to the right. (e) It would spread out. (f) It would get closer together. (g) It would stay the same. (h) Something else would happen. A. The mask is moved a bit to the left. (5 pts) B. The bulbs are moved upward a bit. (5 pts) 3d CTION POINTS Dr. E. F. Redish Exam 2 (M.U.) Pmpcctiva View 1.3 You are viewing the image of a small object (shown as a little arrow) with a spherical mirror. The point marked with a dot is the center of the mirror. Carefully construct a ray diagram to show where you would expect to find the image. (10 pts) If the radius of the mirror is 20 cm and the object is placed 30 cm from the mirror, how far from the mirror will the image be? (5 pts) lbcm Vi J ION (9)051 POINTS A) NAM Physics 122 i 7 i ' Dr. E. F. Redish Spring 2006 Exam 2 (M.U.) 2. (15 points) A long straight jetty that is used to keep a calm, wave—free harbor available for‘ boats has had two holes broken into it by a storm. A series of long wavefronts parallel to the jetty strike it giving rise to outgoing circular waves through the holes. A set of such waves is shown at a particular instant of time in the figure at the top of the next page. A fisherman watching various boats for a while after this picture was taken notices that some of the boats oscillate up and down a lot as the waves pass them and some oscillate almost not at all. The boats are labeled A, B, C, and D. (Take their positions as being at the center of their indicating letters.) Rank order these boats starting with the one that has the largest amplitude of oscillation to one that has the smallest. If any two are nearly equal, indicate that. Thus, your answer might look like W > X > Y = Z to indicate that W had the largest oscillation, and Y and Z had the smallest oscillation and they were equal. If you expect a boat not to oscillate at all, indicate by writing, for example, Z = 0. Put your ranking in the box below the picture and in the space below that, a brief explanation of your reasoning. ,~ _ q ,1 7 A w”, v k i“ :3 ,4 cm 01 (C mat {grate WWW” Wm “if: «a? 31L ,. anti at.» get? w? W V I) \ “gt/01%;} alfalfa Maya. {and ts: tiara always minim fl/Mm my will Mar garage/4mm lay »»/ I - VIN Mai/e r/ If you need more space, continue on the back and check here. [:I ‘ SECTION 0‘: POINTS! Physics 122 Dr. E. F. Redish Spring 2006 Exam 2 (M.U.) 3. (15 points) The Standard media for distributing computer information these ‘ days is a CD that can hold about 800 MegaBytes (8 x 108 Bytes) of data. Given that one English character (letter, number, etc.) requires 1 Byte of storage space, estimate how many novels can be stored on a single CD. Be sure to clearly state your assumptions and how you came to the numbers you estimated, since grading on this problem will be mostly based on your reasoning, not on your answer. M3 aeéumté a rib/“Val 14515 M 300F653 u gm/ 6,6156% [/50 emu a) Ema 3 qulifi W/QM .1. gm: I l l (5 Wilma . i *1 § ‘. r"“:'1’><9330067 e « was a” W // lib—«j W l Word/"Ania Awmfié} lg++€V9Vd 65,6; jfli ale/47161466 “Wig Pegged #5 i937”; “’75 +1) +5 Wm “WM #3 +4 at 5+3+ at +9 +A/ t6 ” ‘35” 79/ 5 Were/e Mai-rd an average 95 e W (5 Jaw/WM) 2:2 L9 OQOWW 01/8) Z43 5 5x108by+ee Meiji” ‘ I wégflgmal/ l by +9 Wkafl Wilma-st flat/95 <4 x ml l ifuh If you need more space, continue on the back and check here. I: CTION POINTS Physics 122 Dr. E. F. Redish Spring 2006 Exam 2 (M.U.) 4. (10 points) In lecture and lab we demonstrated rather conclusively that the ray model of light (and Newton’s particle interpretation for generating it) is wrong. Yet we still spent Considerable class time on it. Why do you think this is so? Discuss the value of teaching and learning the ray model of light. Note: This is an essay question. Your answer will be judged not solely on its correctness, but for its depth, coherence, and clarity. k ‘ Eéglam E if? ‘ . f1./ 1. "V' . . i m . r. "’ 5 ~ . § 7/. f i {4- {a " - “1!: I 1M1 I. V 5;“ dm «5mm, " r oh filioggflme - IQ F ' J“ i i. M F .. (SE) a. 37 chat/fl Méféjihieél 32% it? A .4 hi 3?; wee. If you need more space, continue on the back and check here. D NAMEMECTION POINTS / Physics 122 Dr. E. F. Redish Spring 2006 Exam 2 (M.U.) 5. (30 points) ‘ 5.1 Two large thin parallel sheets of charge are separated by a distance d, small compared to the size of the sheets. The distance d is small enough that the sheets I can be treated as if they were infinite in extent. The amount of charge per unit area on the sheets are +6 and —0 respectively. a? , On the graphs below, sketch graphs of the electric field and electrostatic potential ~ as a function of x. (The places where the axes cross is (0,0).) (10 pts) A V; E0? 3:; .+ e E4“, _ g I I ._/ a“ Q / 5 § é” 5.2 If the distance between the plates is doubled, what changes? Select from the options below and explain briefly why you think so in the space at the right of the answer box. (5 pts) (3) The electric field halves and the potential difference remains unchanged. (b) The electric field stays the same and the potential difference doubles. (0) Neither the electric field nor the potential difference change. (d) Both the electric field and the potential difference double. 0/ (e) Both the electric field and the potential difference are halved. r; 2 0% (f) Something else. ‘ .n " bafié’d 0V1 A Vs» E of ti: l fl Z . ‘ VON/t aim»:th d, AV XV%E&5€ b Wheat aim gamble? @in 3:3 if: [a WW"; ":g] 5.3 In the figure at the right is shown a circuit with three bulbs and a A; V/ V battery. The bulbs have the resistances RA = 3R, R3 = 2R, and RC = R. . The battery produces a voltage difference AV = V0. Find the current . {:31 through the battery expressed in terms of the symbols R and V0, (15 pt k 3 3 w . 7 h.‘ a If you need more space, continue on the back and check here. W m .50 a a w t L .1. +4 a, I avg-gt. a w \ ~ ' a r» J an“: a M I mfg/I" ' If? rm :2... 1‘ $1" . 2'2 ...
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