Gen Physics IIA
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Date Created: 10/20/15
i Electric Currents Ch 18 I So far we ve looked at stationary charges electrostatics now we re ready for moving charges TABLE 18 3 Summary of Units Current 1 A lCs Potential difference 1V 2 H C Power 1W 1 Us Resistance 1 Q 1 VA sngmrio The Electric Battery 181 Source of voltage or potential difference I can make charges move 4 Terminal Terminal lnwiltuiiin quotl Still39uric acid SW 71 t r20 amp Symbol for battery Current b battery SW 71 t r20 i Electric Current 182 symbol isI flowing charge SW 71 t 120 Electric Current conventional current direction a positive charge would flow Conventional Electron current flow gt lt Device Clll39l39EHI Electron current SW 71 t r20 Ohm s Law Resistors 183 metal For a metal conductor I x V Z 7 a 0 resistance Ohm 2unitof bb resistance quot quot SW 71 t 120 nonohmic device Resistor Color Code Calm Niiiulnr Miiliiplirr Tllll39 l kl39 c I re u I Black 0 1 symbol Brown 1 lu i R a 2 3 39 Firsi digll V L Second Lligil r 39V mi Multiplier 11 iiiquot 11 Tolcmnu 39 39c 71 l N0 coin 1th what is the resistance of this resistor 5 Wm 7 Try some others Ch 18 Problem 11 u A 12 V battery causes a current of 060 A through a resistor a What is its resistance b How many joules of energy does the battery lose in a minute SW 71 a 10 8 Resistivity 18 4 p resistivity L length of wire 11111 111739 will llr illly i illl imi 1 11 A crosssectional area SW 71 a 120 g s Ch 18 Problem 12 I What is the diameter ofa 100m length of tungsten wire whose resistance is 032 9 SW 71 a 10 1 0 g Electric Power 18 5 Power Energy time energy transformed QV P V time Other useful P I V IR 2R forms 7 P IV KV o R SW 71 a 10 1 1 a Ch 18 Problem 29 u a Determine the resistance of and current through a 75W lightbulb connected to its proper source voltage of 120 V SW 71 a 10 1 2 Ch 18 Problem 32 I You buy a 75W lightbulb in Europe where electricity is delivered to homes at 240 V If you use the lightbulb in the US at 120 V assume its resistance does not change how bright will it be relative to 75W120V bu bs Hint assume that brightness is proportional to power consumed SW 71 a r20 1 3 a Ch 18 Problem 33 I How many kWh of energy does a 550W toaster use in the morning if it is in operation for a total of 15 min At a cost of 90 centskWh estimate how much this would add to your monthly electric bill if you made toast four mornings per week SW 71 a r20 14 a Power in Household Circuits 186 Wires heat up at a rate equal to PR power fire hazard if is too large fuses prevent overloads by breaking circuit short two wires touching SW 71 a r20 1 5 i Fuses fuses that need to a ll be replaced circuit breaker breaks circuit with a switch a ll ml l swzmuso 16 l Household Circuits What is the total current draw by these devices If the circuit has a 20A fuse will the fuse blow SW 71 a r20 1 7 u Alternating Current 187 DC direct current current is constant I alternating current current varies like a sine wave v frequency usually 60 Hz 60 cycles per second Equations are valid when you 39 use RMS values g 9i SW 71 a r20 l 8 Human Nervous System Amn 397 Mythquot 4me mm uman Nun cudmgs n mum A M mu cum Irumu w my swam zaus Punch mm mu m SW 71 a r20 r T IquiLlc Tum mm knnng Aumu ymrnliml mlenlml Kinematics and Mechanics m 0 vomt 1 1201th Um t m 1 amt 1 113 2amm 7 m0 y yo voyt 12ay252 11y voy ayt v3 U32 2am 7 yo 2Fm mam EFy may F0 mvz r Gmlmg F9 T PEg mgh KEtmm 12mU2 p mu AP F At p K t Electrostatics kqlqz F 7 1 q1q2 F 7 4713960 72 E E q a 7 kQ T2 APE 7W PE iPE 7W Vba Vb 7 Va 1 b 7 ba q q APE q AV Vba E d V kg 1 Q r 4713960 T Q C V A C 603 A 7 Ed PE 12QV 12CV2 122 Currents AQ 1 E V I R L R pA v2 PIV12R R ReqR1F2R3EiRi 1 7 1 1 1 7 E 1 Reg 7 R1 Rz Rs 7 1 Bi Ceq 01 02 03 2i Ci parallel 1 1 1 1 1 2 Ceq 01 Oz 03 1 Ci semes V0 eetRC Magnetism F IZB sim9 F qUB sim9 MO I B 27139 r uo 11212 F 2 27139 d N B MOT 13 BACOSt9 AQB E mf At AltIgtB E 7N mf At Emf NBwAsinwt VS 7 NS Vp NP 1 7 NS 5 Np Waves U fA FT U mL I x A2 1 47mg 71 L7T 8671192 U2 8671191 7 U1 A 19 z L Sound Us 331 060T ms I 1OZ 3 0910 7 UiUo f ifo Uivs Geometric Optics if 1 171 do dii hi di m ho d0 C n U 711 8671191 712 3671192 Light as a wave 1 31710 m A 1 31710 771 12 A D 31710 m A I 0 603219 Special Relativity 1 Y 7 N17 11262 Ato At At 17 11262 Y 0 L0 LL0117 U262 39Y moU p mo 176 26 m39rel Ymo 2 E0 mot2 KE V71m062 E KE 1 mocz 39ymocz E2 pzcz 771364 7 U 1 1 U LLCZ Quantum amp Atom AP T 290 x10 3 m K LL Enhf Ehf 7E hf h pf 13 7 c 7A AE p 1365V n n2 En 7136 eV 5 Constants G 667 x 1011 N mZkg2 k 90 x109 N mZCZ 60 885 x 1012 CZN m2 1eV 16 x 1019 J 110 47139 x 107 TmA US 331 060T ms 0 300 x108 ms 0 1012 Wm2 1amu 111 16605 x10 7 kg 9315 MeVc2 15V 160 x 10 19J h 6626 X10734 J 8 m5 911 x 1031 kg mp 167 x1047 kg Speed of Sound TABLE 121 Speed of Sound in Various Materials Different in different materials Zo cand latrn I V ms Mnlcrlul SpecdIIIIJ Air 343 In aIr at 0 C and at 1 atm Airll C 331 Helium 1005 temperature dependence Hymn W v 331 060 T ms WWquot 1 Sea water lSFIU ran and sleel Sllllll Glass 5 Aluminum Sllll Hardwood Concrele ywlz 1 Characteristics of Sound Loudness intensity energy per area per time Pitch high or low frequency Audible range of human ear 20 Hz to 20000 Hz 3 1227 Decibels Intensity of sound is measured in decibels range of 1012 between intensity of quietest and loudest sounds we can hear ear hears on logarithmic scale decibel measure of intensity I 311391 dB 10 logI 0 391l l39 In 10 X 10712 quot1112 MM 1227 3 Intensity TABLE 122 Intensity of Various Sounds Sound Some Lml llllenbily nfllIoSmIIId dB IWm lcl plane m 50 m Hll IIIII TlIrcslInld ul min IZO I Loud rock Concert ill I SIrcn mznm 101 I x In 3 Am iIIIcrioI39 ill JllkmII 75 3 x In Busvslrecl IrIIflic 70 l x III TalkAIII 50cm n5 3 x In quot UuIlediu 40 I x 10quot Wlmpux II I x In Rusllc ancavclt In I gtlt IIr 39IIIrcxImIan hearing 1 I x Illquot 3 127 Human Ear Stirrup Skull 39 Hummer imulcuculau mn11 Mulilm39y mum 39 m llu hmm 39 r W 7 v 3v 4 A 39 i nquot 4 I quot nclllcd U E39lr umuunm 1an i 1 Tymwnnm quot leill39dl llllll Owl indnw A Rullml wimluw I chl lllll Lur twain rvguus Damian Wm M W Main 1227 5 Frequency Response of Ear Pl Tlrni IFNdMP Ei llOphuns 7 A 00 lm J40 03 RD WJ HV quotE E J 3 L 30 1 0 m4 1 g 40 4i m m7R 2 V W70 20 Vquot I V I040 0 1039 l l l l 10 50 mo 500mm sum39nroo Frequency Hu Cumrlqlvl l Psalm Prunlm Hall in 39 1227 Sources of sound string instruments l J I sound FumImmnmmamliurmmnmi sounding box quot quot MI sounding board l 7 r 7v 7 Flhl Uuuhmu ur wcumlMinimum1 2 H K quotI quot Ligjq Srmnd incnnnc m munme I 3 umtza 7 Ch 12 Problem 78 A highway overpass was observed to resonate as one full loop when a small earthquake shook the ground vertically at 40 Hz The highway department put a support at the center of the overpass anchoring it to the ground What resonant frequency would you now i expect for the overpass Earthquakes rarely do significant shaking above 5 or 6 Hz Did the modifications do any good 3 127 7 rug 5 9777 1 Bcltm nunllliiuuuu Adam llppml Mm inullll39mnnm Sources of Sound Wind Instruments TUBE OPEN AT BOTH ENDS u DiAplucemcmnl nir L Firsl hurmnniu l39undumcnlul A node i B i o 9 lmulionut39airmuleculcs A Secmld Imrnwnic E f 39 A Third harmonic gtltgtltgtlt39 fr B 39 I V Copyright 2005 Pearson Prentice Hall lnc Overmnes WM 1227 Closed at one end TUBE CLOSED AT ONE END 6 Displacement ol39zlir 39 First harmonic fundamental LL 39L If JL Third harmonic Overlones Fifth harmonic 5 V f1 Copyright 2005 Pearson Prantlce Hall Inc WM 120 10 Quality of Sound CliilimI Plum l L o l u 39 n mun 1mm 3mm H mm 2000 mun u mun 30m mintnay lHIl Frequency HI I39Inplvnq lllzi Copyngm 2005 Pearsun Pranuce Hall Inc Violin 3000 Interference amp Beats 50 Faun mm Y VW mm iii WNWV WWW Utm ll mt bill s A VV A V V upyngm 2005 Pearsan Prentice Hall Inc fbeats fA 39 fB 31 127 12 v Doppler Effect lil e l l 2 A1 rcxl h Fircu uck moving Copyright 2005 Pearson Premise Hall Inc lliiiirm i Doppler Effect U l U0 7 JPNE v speed of wave v0 speed of observer vS speed of source emitted frequency f observed frequency lf gtf0 s and o approaching I f lt f0 s and o receding lower higher frequency frequency gun4227 13 maize 14 amp Sonic Boom Ultrasound Imaging 747L3939 L llnumal Imm um 4mm um Curlylaid 005 D Z Ystlllp f39llll HAquot lnr I My 1227 delay of echo indicates distance to boundary 3 1227 color reflects strength of echo i Magnetism Ch 20 M 5 4 d5 ii Repulsive S r is Ni lt7 N S S N P 739 Repulsive No magnetic monopoles mm 1227 1 ii Magnetic Field Lines direction of magnetic field B is perpendicular to field line number of lines per area is proportional to strength of field field lines point towards N field lines form closed loops B lmm m rim v Earth s Magnetic Field Rowlian kll l 393 quot magnetic declination r 1 gnu c TEL 11qu angular difference I between geographic north and magnetic nonh varies with latitude ic pnlc up it Ih Mugnul iu 701k mm 1227 3 Electric Currents amp Magnetic Fields Electric current produces a magnetic field Hans Christian Oersted 17771851 Electric current exerts force on magnet Direction of magnetic field given by Right Hand Rule i Magnetic Field of a Current Loop Units of Magnetic Field 0 Tesla SI 1 T 1 NA m 0 Gauss cgs 1G1O394T Earth BO5G BO5X1O 4T mm 1227 5 I Force on Current in B Field l3 Righthind mlx in Copyright co 2005 Pearson Prentice Halli lrir F IlBsz nH for uniform field Direction of F given by Right Hand Rule fingers obend fingers B thumb F Ch 20 Problem 1 u a What is the magnitude of the force per meter of length on a straight wire carrying an 840A current when perpendicular to a 090 T uniform magnetic field I b What if the angle between the wire and field is 4500 mm 1227 7 Specifying 3 Dimensions 0 out of page 0 tip of arrow 0 into page 0 tail of arrow 3319454125 3 F qusinQ i Force on a moving charge Right Hand Rule qvfingers B bend fingers Fthumb mm 1227 e in uniform B field X x x x x X X X X X X X X X mm nl ulcclrnix I ix mm 1hr page 9 Ch 20 Problem 11 I Find the direction of the force on a negative charge for each diagram shown 3319454 1227 ThinkPair Share Derive an expression for the radius of an e s orbit in a uniform B field Express your answer in terms of me v qe and B mm 1227 Equation gives magnitude of B RHR gives direction permeability of free space no Magnetic Field of long straight wire BH0 27139quot it yo 47139 X 10 7 T IllA may 1227 Ch 20 Problem 28 Indicate the direction of B due to the current carrying wire at each of the points C D and E in the plane of the page C l 3 magma 13 Two long wires are oriented il Ch 20 Problem 43 so that they are perpendicular to each other 10 cm At their closest they are 8 17 f l 200 cm apart What Is the 109 cm magnitude of the magnetic field at a point midway between them 39 T 3319454 27 Bottom wi re IT 200 A L 1350A Force between 2 parallel wires III 12 1H 1 F2 2 IgBllz Z l i 27r d 2 I Fz l i Q l l w l 7 z 393 n Nwlnf rr nlerwll in magma 15 F ind direction of force from it 7 RightHandRule Ill la Ill 112 new 1227 i Ch 20 Problem 44 Two long straight parallel wires are 15 cm apart Wire A carries a 20 A current Wire B s current is 40 A in the same direction d Determine the force on wire A due to wire B and the force on wire B due to wire A magma 17 i B Field of a Solenoid A solenoid is a long coil of wire The field inside the solenoid is B toIAVl where N number ofturns length of wire Electromagnet is a solenoid with an iron core increases magnetic field bc iron becomes a magnet 3319454125 18 Ch 20 Problem 48 u A think 12 cmlong solenoid has a total of 420 turns of wire and carries a current of 20 A Calculate the field near the center magma 19 Ferromagnetism Ferromagnetic material Random Preferentiany iron or other materials that can downwards be made into magnets You can make a magnet from iron by placing it in a strong B field individual domains become aligned with external B field Loss of magnetism from dropping heating Curie temperature 1043 Kforiron 3319454125 20 Mass Spectrometer Used to identify atoms and their concentrations in a sample of material between 81 and 82 molecules go straight if q E q v B or v EB after 82 B produces circular motion q v B m v2r mqB rvqBB rE Found isotopes LI Detector or lm magma 21 il Ch 16 Electrostatics electric charges that are not moving Definition of new symbols e39 electron p proton n neutron e positron g Coulomb s Law FZkotog 7 2 u k 90x 109 N m2C2 Coulomb s contant Q1 Q2 charges measured in Coulombs C 1 C is a lot of charge r distance between Q1 and Q2 i k Q1 Q2 Electric Force r2 Similar form as gravitational force weird huh except positive and negative charges Like charges repel opposite charge attract I Figure 16 13 h Flgure1615 39 l lt3 lll r 157 F k Q1 Q2 l Charge Carriers 7 2 The electron 1e39 1 602 X 103919 C smallest unit of charge also referred to as e negatively charged Charge of 1 e39 is 1e The proton 1p 1602 X 103919C positively charged Charge of 1 p is 1e Charge is quantized a ThinkPair Share What is the electrostatic force between an e39 and a p in a Hydrogen atom given the radius of the H atom is 05x lO391O m Coulomb s Law with different constants 1 Q1Q2 471150 7 2 6 permeativity of free space 1 71 2 I 2 U j 88 gtlt1ll C Jm 7 more relevant to future chapters i Illustrations of Coulomb s Law Comb amp Paper v5 Illustrations of Coulomb s Law Electrosoope gt01 5 x x L 1331 t gt 5 quot Mt III II It a I It induction Illustrations of Coulomb s Law Van de Graaff generator amp pie plates Conductor versus Insulator Conductor Insulator a 7 Neutral metal rod if xii V V Nonconducto r b Metal rod still neutralt but with a separation of charge charge separation within molecules e s travel conduction Illustrations of Coulomb s Law Flowing water amp charged rod Q Jy I DC Circuits Ch 19 Circuit symbols Battery Capacitor 0r Resistor JVW V re Switch Ground a 9m Build these two circuits FNii w VAEI AE 31 Lin 1 3 Series j i J m II 7 m A V M B nus p A i Til A IV Parallel i ni7ii 3 37 llfx f How does i l u Req compare L 4 between two L 3 7 7 Li circuits l till ll Shampialz 2 Adding Resistors In series 52 wig41227 1 Measure current and calculate Ri M quot2 N 9 i F RNI F Wi vi quotl iquotv39 iwv 39l i i i r ch Series quoti quotI 3 I m ll lh Emmy l m 1quot r CapY4th z zuus F L zrw F ren im Hall lru quotw Parallel iiiw Hint First calculate war Req l iii Sea 319am 27 4 Ch 19 Problem 17 Determine a the equivalent resistance of the circuit and b the voltage across each resistor 53912 mat41227 5 I Emf and Terminal Voltage Emf g potential difference across battery terminals when no current is flowing stands for electromotive force but not really a force Terminal Voltage model real battery as emf plus resistor r VA quotInf 1 739 Terminal wings lh 53912 mat41227 6 I Ch 19 Problem 1 Calculate the terminal voltage for a battery with an internal resistance of 0900 9 and an emf of 850 V when the battery is connected in series with a an 81 09 resistor and b an 8109 resistor 53912 mat41227 7 ll Kirchhoff s Rules G R Kirchhoff18271887 First Rule Junction rule at any junction point the sum of all currents entering the junction must equal the sum of all currents leaving the junction conservation of charge Second Rule Loop rule the sum of the changes in potential around any closed path of a circuit must be zero conservation of energy 53912 mat41227 3 l Junction Rule Loop Rule 309 H 4009 h 2909 k h H AAAA VVVV r 1 11 r 52 uv 1 it 40 o 13 1 2 45V AAA AAAA I I3l1l2 a vvvv 39 vvvv 39M d b c lt 1 l I r gt 9 V quot 2 80 V 1 Q n V ll AVAVAVAV e a b c d e I M g m f e 400 M39 Him Sam 2 9 Swan 27 1o Ch 19 Problem 25 Capacitors in Parallel a What is the potential difference between points a and cl l l Q1 30 h F AVA AVAV a I I 2 b Qlll 40 52 1x I Q 43 v d AVAVAVAV AVAVAVAV I a d quot lt 1 I lt3 3 20 9 Q3 3 30 V 1 Q gt nl A A It ll v v v v t 52 mm 1227 52 mm 1227 I Capacitors in Series C C C alA3B3 M ll I Q1llQ QnQ erQ 1 1 1 1 ECTEE 53912 mm 1227 I Ch 19 Problem 35 u a Six 47uF capacitors are connected in parallel What is the equivalent capacitance b What is their equivalent capacitance if connected in series 52 mm 1227 I RC Circuits Resistor and capacitor in series Applications windshield wipers pacemakers camera flash timing of traffic lights 52 mm 1227 Ii RC Circuits O 1 RC ZRC 3RC I Timu mm Hall in 1 In in mmgm r arm Pmm 52 mm 1227 i RC Circuits Ch 19 Problem 69 I E RC time constant time to reach 63 of maximum voltage I A heart pacemaker is designed to operate at 72 beatsmin using a 75uF capacitor in a simple RC circuit What value of resistance should be used if the pacemaker is to fire V13 capacitor discharge when the voltage reaches 63 of its maximum lll samaauza 1a I Electric Hazards ll Electric Hazards Lethal current 100 mA causes ventricularfibrillation Larger current 1 A does not stop heart causes burns Resistance of human body 104 106 2 when dry 103 2 when wet I when one hand is on electric keep other hand in pocket I NEVER go near downed electric wires ground can be charged stand on one leg or run samaauza 19 5 mm 1227 20 Ch 21 Electromagnetic Induction If electric currents produce magnetic fields can magnetic fields produce electric currents Yes Discovered independently by Joseph Henry American Michael Faraday English I Joseph Henry Lived from 1797 to 1878 Premier American scientist after Ben Franklin Albany native Attended amp then taught at Albany Academy conducted experiments in his spare time Invited to Princeton and stayed there now endowed chair of physics department Joseph Henry Laboratories First Secretary of the Smithsonian Institute One of first members of National Academy of Iron Science Induced EMF Induced EMF 1 Gulvunomeler 3 I Faraday observed deflection when switched was opened and closed changing B field induces current much up I Nu IUWLIHJ cm H Inpwmcm 39 39 n Inuuil comm 3319454 4 V Faraday s Law of Induction 39 Faraday s Law of Induction I The induced emf depends on the If circuit contains N closely wrapped loops area of loop how fast B field is changing Em 4 ATSquot change in magnetic flux 13 Faraday s Law of Induction Can induce emf by changing B field area of loop loop s orientation with respect to B field where I B 84 Z BA 0le mm 6 Ch 21 Problem 5 Lenz s Law I A 120cmdiameter loop of wire is initially A current produced by an induced emf moves oriented perpendicular to a 15T magnetic in a direction so that its magnetic field field The loop is rotated so that its plane is opposes the original direction of change parallel to the field direction is 020 s What is Test yourself the average induced emf in the loop N n Copyright 0 2005 Pearson Prentice Halli Inc mm a More practice I What is the direction of the induced current in the circular loop due to the current in the i Ch 21 Problem 2 u The rectangular loop shown is pushed into the magnetic field which points inward In what direction is the induced current Wire fill l gt l fA luni39li hummtg l l c x t V V m lhl M Li Copyright 2005 Pearson Prentice Hall inc mm 9 maga 1o i EMF Induced in a Moving Conductor O 7 l Area inside loop is increasing as rod moves to right AJ iv AI A11 I AI E 7 Art 7 BAA 7 Bm quot A1 A quot A1 Emf Bll39 Electric Generators 3 Axle rotated X 73mm IV indiccd n lur Bx me l l aw 12 i Ch 21 Problem 20 u A simple generator is used to generate a peak output voltage of 240 V The square armature consists of windings that are 60 cm on a side and rotates in a field of 0420 T at a rates of 600 revs How many loops of wire should be wound on the square armature l Transformers r iP VP VsNs ABAt in primary induces V8 in secondary coil I P VP mmi IUI39IIS llllll Works for AC only DC voltages don t have Laminated Changing B field 1 COI39C a 13 pm 14 Transformers StepUp Transformer vs gt VP coil and 120 in the secondary coil What kind I StepDown Transformer of transformer is this and by what factor does V lt VP it change the voltage By what factor does it s change the current Conservation of energy requires I PP P5 IF VP IS v8 15 Np 1P 9 NS mm 15 mm 16 Ch 21 Problem 31 u A transformer has 320 turns in the primary Inductance Coil 1 Coil 2 I il SelfInductance A11 changing current passes through a coil E7an IT produces changing Bflux y t which induces an emf A12 Induced emf opposes change in flux E39mfl I At 39 E f L AI m s where M mutual inductance At Units of inductance Henry 82 1 H 1 Qs induced Inductance H ms 17 33194 13 Ch 21 Problem 39 u If the current in a 180mH coil changes steadily from 250 A to 100 A in 350 ms what is the magnitude of the induced emf mm i Electromagnetic Waves Ch 22 James Clerk Maxwell Prediction of EM waves culmination of EM theory unified electricity and magnetism Extra Credit research life and achievements of Maxwell write a brief summary 1 page mm 1227 1 I Maxwell s Laws 1 a generalized for of Coulomb s law Gauss s Law I 2 a similar law for the magnetic field except magnetic field lines do not begin or end I 3 an electric field is produced by a changing magnetic field Faraday s Law I 4 a magnetic field is produced by an electric current Ampere s Law or by a changing electric field my 1227 2 Seen on TV Faraday Flashlight Never Needs Batteries or Bulbs The Faraday Flashlight uses no batteries or bulbs Instead it uses your energy and induction to produce a bright light using efficient LED technology Just shake the light for about 30 seconds and the Faraday Flashlight will provide about 5 minutes of light During prolonged use it can be shaken for 1015 seconds every 2 or 3 minutes giving you an unlimited supply of light mm 1227 3 Production of EM Waves a changing E produces B u a changing B produces E which itself is changing which produces B which produces E which produces B which produces E and so on Result is a wave of electric and magnetic fields that propagate away Meat4127 4 V Producing EM Waves lconstant no waves lchanging waves mm 1227 il Propagation of Waves 2 Plane waves far Nearfield from source 6 IS complex Dirccnnn 04 ul l l39 ll391 cl 1 Antenna a h E and B oscillate in phase an perpendicularto each other Also perpendicular to direction of motion Mpg 1227 6 Ch 22 Question 1 u The electric field in an EM wave traveling north oscillates in an eastwest plane Describe the direction of the magnetic field vector in this wave mm 1227 Speed of EM waves Maxwell showed that speed is given by E 1 B v 60 391 1 300 X 108 IIIS Light is an electromagnetic wave Previously wave nature of lightwas known but didn t know what kind of wave light was EM waves first detected by Heinrich Hertz f 109 Hz 3319454125 3 Ch 22 Question 3 Can EM waves travel through a perfect vacuum Can sound waves mm 1227 9 Electromagnetic Spectrum Wm39cicnglh 4m 1 In x x W m 394xlii H 15xllll Hz Visith light Cnpyrighl 2005 Pearson Prentice Hall Inc 3319454125 10 Ch 22 Problem 5 I What is the frequency of a microwave whose wavelength is 160 cm Max125 11 Radio Communication Amplitude Modulation AM Program audio Total signal AM Cumnghi m suns Punishquot Pmmlcu Hall in 3319454125 12 Radio Communication Frequency Modulation FM Program audio VVVVVV C urricr Total signal FM 39mmgm w aim Psaisrn pmm Han in mm 1227 i39 Ch 22 Question 13 u A lost person may signal by flashing a flashlight on and off using Morse code This is actually a modulated EM wave Is it AM or FM What is the frequency of the carrier wave Myst 1227 14 g Wave Nature of Light Ch 24 Christian Huygens 1629 1695 contemporary of Newton developed wave theory of light Huygen s Principle Every point on a wave front can be considered as a source of tiny wavelets that spread out in the forward direction at the speed ofthe wave itself The new wave front is the envelope of all the wavelets tangent to all of them mm 1227 Source 0 S Vs Huygen s Principle Diffraction Huygen s Principle is useful for understanding diffraction the bending of waves behind obstacles into the shadow region t39 l gtgt lcl Copyrigmig 2005 Pearson Prentice Hall lnr mm 1227 Interference Thomas Young 1773 1829 defin itively at least temporarily RMquot demonstrates wave nature of light Young s DoubleSlit Experiment Wan lmnk 5mm 3319654125 gt mi til Wm Pmmm Phi in Scrum Interference I umdummc 7A lhl mm mm Fem Hal W Constructive interference m 012 m order Destructive interference Source must be coherent waves at 81 and 82 are inphase mm 1227 I what you see on the screen Constructive 7 1nterference m 3 1 9 l 2 3 Destructive interference i quot12 I O i l cww EDUSW mm Hlil lnl 3319454 1227 Ch 24 Problem 1 Monochromatic light falling on two slits 0016 mm apart produces the fifthorder fringe at an 88 degree angle What is the wavelength of the light used mm 1227 Conceptual Question LIZUin What happens to the interference pattern if the wavelength of light is increased from 500 nm to 700 nm What happens instead if the wavelength stays at 500 nm but the slits are moved farther apart Meat4127 Ch 24 Problem 5 Light of wavelength 680 nm falls on two slits and produces an interference pattern in which the fourthorder fringe is 38 mm from the central fringe on a screen 20 m away What i39 Visible Spectrum L l l l l l l l l 400 nm 500 nm 600 nm 700 nm is the separation of the two slits 139 l l l Hint tan 6 e for small angles and angles 739 X 390 HZ 6 X W4 3 X quotWW 4 X 390 HZ t ConyngthQDOS PearsoiiPrenlIce Hell inc mus 33quot643941217 9 awearm 10 Dispersion Index of refraction varies with wavelength of light As a result white light is separated into component colors by a prism or by water rainbow magma 11 Dispersion amp Rainbow m copynqmo 2005 Pearson Prenlice Hall in red is bent the least red light reaches observer s eye from higher water droplets violet light reaches observer s eye from lower water droplets 3319454125 12 Diffraction by a Disk Diffraction by a Single Slit Shadow lafl1l h39inHCV imma imma lirxglii om Briglii 39 um mimignin i runs mmm Pmm mix Inc lnlcihil Bright spot Lam qlii zuushamw Valium in Dsin6mk m123 Diffracted light interferes constructively at center of shadow 7 V 7 V M M L n A v 11 I 9 requires a p0int source of monochromatic light e g laser I magma 13 Diffraction Grating Diffraction Grating I b f I double slit versus for multiwavelength a arge num ero equally spaced parallel PAMsine diffraction grating light slits same relation as doubleslit sin 6 m A d m0 1 2 produces sharper and narrower interference patterns that double slit ml 1710 Inl m 1710 ml amaze 15 moiarm 16 Interference by Thin Films 3Q Produces rings of constructivedestructive interference A C Air u D B Water nw wt w t mm 1227 I Polarization Polttl39izcr Unpolztrized Polarized light light Ligh1gt direction 0 ill PDiLtI39iICI An39tl 39zct axis Verlicul axis horizontal Light No light direction Unpolztrized Platteqmlurized ight lwht Capynght c 2005 Pearsan Prenltce Haii lrtc Polarization by Reflection reflected rays are polarized in plane parallel to reflecting surface Brewster s angle polarization of reflected light varies with angle of incidence 0 polarization at normal incidence I 100 polarization at Brewster s r v 39 angle tan 6p n2n1 mm 1227 Polarization Vil lit ui Horiitmlul I When passing light pu LII39Ich 45 pa ttrtzer through more than one polarizer ocosze where I0 incoming intensity e angle between the Light polarizertransmission directly axis and the plane of polarization of the I incoming wave Meat4127 Geometric Optics Ch 23 Ray Model assume light travels in straight line uses rays to understand and predict reflection amp refraction This bundle enters the eye mat41227 1 I Reflection Law of reflection the angle of incidence equals angle of reflection angles measured from normal Nonmtt Ntimml It urlttw n url th l l l l l l 5mm Angim Angina Anglenl Angle of l l tutmm mustum lnk39ldenuei re ection l l Incident lighimy Lquot l s chmcd t J v 1quot light my 39 tquot t l h Copynqm to 2005 Pearson Prentice Halt lnc 3319454125 2 Reflection Diffuse reflection Specular reflection mt Copyright 2005 Pearson Prentice Hall lnc mat41227 3 Ch 23 Question 1 I What would be the appearance of the Moon if it has a a rough surface b a polished surface Meat4127 4 Plane Mirrors Plane m l rror Re ecting Cnnynrjhl m was warm Pr nllra Hall lw mm 1227 5 Spherical Mirrors Normal gt to surface Rays from distant source Convex a mirror 9 N ormal N L to surface ancavc b mirror Cupyrlghl o 2005 Pearson Frenllce Hall Inc Focal Point amp Focal Length Parallel rays striking a concave mirror come together at focal point mm 1227 7 Image Formation la Ru 1 gncmm lrnm 039 ll mlhum mm L cm through li rm Ray 2 gum through V pzlmllul n my In r 2W5 Pcnrauu w Mum mm u 39a 127 Mirror Equation amp Magnification I Ch 23 Problem 8 I How far from a concave mirror radius 230 cm must an object be placed if its image is to be at infinity aimarm 9 33194541217 10 Convex Mirrors Refraction Virtuai image index of refraction n can t detect on paper or Numui screen Nnmui Source i 37 lnLiduI 0 my Sign Conventions object image orfocal point on reflecting side of mirror Rcimcmi i faintmi m i n i Au tlii 7 Airtiigi l nair 1 Wuul lt Rum Merl1 my 1939 IiXCidcnt has a p05itive distance I n Iass 15 I my g Reimcied 3 Sum Anything behind mirror has my 3 LL negative distance ii i I Snell s Law in nit hcmixmwurg i image height is positive if upright negative if inverted relative to object gt n2 4 mi away from i magma 11 3319454125 12 i Indices of Refraction TABLE 23 1 Indices of Refraction Medium I cv Vacuum 10000 Air 211 ST 10003 Water 133 Ethyl alcohol 136 Glass Fused quartz 146 mwn glass 152 Light flint l 39 Lucite or Plexiglas 151 Sodium chloride 53 Diamond 2 A 589nm mwm t yaw mu m 641217 13 l Total Internal Reflection Incident angle where refracted angle 62 is 90 is the critical angle at incident angles greater than critical angle light is totally internally reflected Source Ch 23 Problem 31 In searching the bottom of a pool at night a watchman shines a narrow beam of light from his flashlight 13 m 3 above the water level onto the i surface of the water at a point 7 27m from the edge of the pool Where does the spot of light hit the bottom of the pool measured from the wall beneath his foot if the pool is 21 m deep T l 641217 15 Ch 23 Problem 32 Light is incident on an equilateral glass prism at a 45 degrees to one face Calculate the angle at which light emerges from the opposite face Assume n158 9654125 16 Ch 23 Question 7 Thin Lenses What is the focal length of a plane mirror A 4 x 39i i quot i l l What is the magnification of a plane mirror ll in I xl l Donblc Planoconvcx Convex r com cx meniscus 8 n Converging lenses x i 9 l i i i ii i l i l l i x I i 39 39 Double Planocnncnve Concave CUHCEWC meniscus h Diverging lenses Limynrilil c anus new mumm mi in Mammy 17 33194541217 18 Focal Length Focal Plane and Power Ray Tracing f focal length luiiii lmc umm i i I Power inverse offocal length P 1f 39 measured in diopter D 1 D 1 m1 ill irtl cumin o mun quotLuann mm m in mm 1227 i Thin Lens Equation magma 21 I Sign Conventions focal length positive for converging lenses negative for diverging lenses object distance positive if the object is on the side of the lens from which the light is coming this is usually not the case otherwise it is negative image distance positive if the image is on the opposite side of lens from where light is coming positive for real images negative for virtual images image height positive if image is upright negative for inverted images h0 is always positive 9654 1227 22 Ch 23 Problem 43 u A sharp image is located 780 mm behind a 650mm focallength converging lens Find the object distance a using a ray diagram b by calculation mm 1227 23 Ch 23 Problem 44 Sunlight is observed to focus at a point 185 cm behind a lens a What kind of lens is it b What is its power in diopters am a 1227 24 Ch 23 Problem 45 A certain lens focuses light from an object 275 m away as an image 483 cm on the other side of the lens What type of lens is it and what is its focal length Is the image real or virtual mum 25 i39 Ch 23 Problem 53 a How farfrom a converging lens with a 500 mmfocal length lens must an object be place if its image is to be magnified 200 times and be real b What if the image is to be virtual and magnified 200 times mum 25
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