MT1_sol - Name: iii—q Am August 12, 2011 Student ID:...

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Unformatted text preview: Name: iii—q Am August 12, 2011 Student ID: Summer 2011 Session C Physics 6C MIDTERM 1 o This is a closed book, closed note examination. 0 Print your name on every page. 0 Pencil is NOT allowed, except for ray diagram. 0 Please work neatly and clearly. Circle your final answer. Don’t forget to include the units with correct sig. figure in your answer. 0 Don’t leave the problem blank. You will receive partial credit for the correct equation even if you don’t know how to solve the problem. GOOD LUCK !!! Part A /10 Part B: 1 /30 2 /30 3 /30 Total /100 Part A[10 pts]. Multiple choice questions. Circle only one answer for each question. 1. Two coils share a common axis as shown in the figure below. The mutual inductance ofthis pair of coils is 6.0 mH. lfthe current in coil 1 is changing at the rate of 3.5 NS, what is the magnitude of the emf generated in coil 2 ? a. 5.8x10'4 V b. 1.7x10'3 v c. 3.5x10‘3 V d. 1.5x10'2 V ‘ @ 2,1){10'2 V soil! will I 2 Which statement concerning electromagnetic waves is false? a. Electromagnetic waves carry energy. @ X-rays have longer wavelengths than radio waves. c. In vacuum, all electromagnetic waves travel at the same speed. d. Lower frequency electromagnetic waves can be produced by oscillating circuits. e. They consist of mutually perpendicular electric and magnetic fields. 3. An electromagnetic wave has an electric field with peak value 250 N/C. On average how much energy does this wave deliver to a surface with area 2.0 m2 in 1 minute? a. 83 J b. 166] c. 2490 I d. 4980 J @ 9960 J 4. At what speed would one have to move at to see a red light as green. Presume red light wavelength = 630nm and green light wavelength = 530nm. "/a. 0.17 c . 0.029 c c. 0.086 c d. 0.41 c e. Cannot be determined ’ 5. The figure below shows the path of a portion of a ray of light as it passes through 3 different materials. The figure is drawn to scale. What can be concluded concerning the refractive indices of these three materials? a. I'll < n; < n3 b. H] > n2 > n; KC. 11; < I11 < 112 d. n; < 111 < n3 8. 111 < n3 < n; Part B. Short questions. Steps and explanations are reguired. l. (30 pts) A 100 W spherical source radiates light in all directions. (Answer inr3 significant figures) a. (5 pts) At 1 m from the source, what is the intensity in the EM wave? ———— n . '\ r'uCz “_I£.».2.€I__: ._____:}7M§L W ._‘ i— mm L /m b. (5 pts) At 1 m from the source, what is the rms value of the electric field? I 3 U’ Ht II k— C -‘ .H7 'ic \(RTTxiu7)(};-NCV) ,. w Mr # W" W _ . ,/ : <T » ‘b gq/x’gj m .‘S Li’ ’ (C VCM\ c. (5 pts) At 1 m from the source, what is the rms value of the magnetic field? firm) _ n 3 - érms g Kb e———- t. s D — -———— = m” 5.— smco : [i-‘igfl/LJ d. (4 pts) What is the total power radiated 10 m from the source? I 1‘) I ‘Y‘ 1 e. (3 pts) If at a particular time, the E-field points in the -y direction and the B- field points in the +2 direction. What direction is the wave propagating? f. (8 pts) If a fully absorbing sphere of radius 1 cm can be supported by light pressure 1 m directly above the source, how much radiation force is exerted on the sphere? [Force = Pressure x area]. ~ _ q ( ’— : rrC‘isbk—wr‘ X WLk : ac ‘ 7A ’ «)L : ‘ 7 L .1— =(i)('H& )‘u‘tttxicl ‘ a 17. ‘ 5% fi/C A] 2. d) a) (6 pts) Draw the ray paths (any 2 rays) and the image. Reflecting surface b) (4 pts) Describe the image: Virtual or Real? .r Enlarge or Shrink? : Y n ***************************************************************** A 3.0 cm tall object is placed 20 cm in front of a spherical mirror. It is desired to produce a virtual image that is upright and 4.5 cm tall. (Answer in 2 significant figures) c) (6 pts) What is the magnification of the image? h ; Lr « S ’— .: _‘ .: ‘ 5 m h“ C I I d) (6 pts) Where is the image located? J"— /' ‘ Z 3 l W1: [.g: :3 (1;: —(_.Iv»>)L1c,):L-_.>C,rm e) (6 pts) What is the focal length of the mirror? 1 cilia In)» \(>Q) I " 1., : ___ I __ A k L, — _ ‘- 5‘ L ,1 li; +d a, - 7> L r 1 c. céi..-.v_r::» f) (2 pts) What type of mirror should be used? .3 CC77C/1UL mirt’tr1 }_.**__‘g,, 3. (30 pts) Consider an ideal light-pipe (fiber optic) with n = 1.4. Light ray A enters perpendicular to the beveled end of the light pipe. (Answer in 3 significant figures) W Internal reflection at. (8 pts) What is the minimum angle 9 such that the light along path A will be trapped within the light pipe? fl").r\C-Lc_ : L‘)¢~)‘r\(1‘bt b. (3 pts) In the figure above, is a ray such as path B possible? iA/‘v l owl—LL41 swift/q, => gp/WLL L4 0V1 ~ 7 ~ t t. V L’A‘nf r111 \INV‘M r0991) c. (3 pts) If the light-pipe is immersed in a liquid with index of refraction 1.6, will it still work? n (4 inc: ‘IU; ‘ I , ~Lt‘TtAwL 3 nP-re < d. (8 pts) What is the velocity oflight in the light-pipe? ’fl .: C‘ . i ; _-__ _ 3 mi, U j’ “ h e. (8 pts) Ifthe light has a wavelength of 550 nm in the light pipe, what is the wavelength in air? h : r /\wl\r ,-\,y 7, :5 /\«X|r :h’l\pipk I ) l'l‘~ 2 [7 flnfil ...
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MT1_sol - Name: iii—q Am August 12, 2011 Student ID:...

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