The electric field in an EM wave traveling north oscillates in an east–west njb7 v s3oex,f:fy)/w plane. Describe the direction of the magnetic field vector in this wjx o:s,y fw)fb3 e/vn7ave.

Is sound an electromagnetic wave? If not, wvf3fhlve,1ki5 ,xva4 hat kind of wave is it?

Can EM waves travel through a perfe,cnn5y3c 7f nmct vacuum? Can sound waves?

When you flip a light switcs6+;quz crhh/32sqzf h on, does the light go on immediately? Explain.

Are the wavelengths of radio and television signals loci sqldi:kn4z1 ty542nger or shorter than those detectable by n21 t4 :idsl4zyi5kc qthe human eye?

When you connect two loudspeakers to r-p :d5c3mv8xxme(s jthe output of a stereo amplifier, should you be sure the lead-in wires are equal in length so cxj8 3 -msed xp(5v:mrthat there will not be a time lag between speakers? Explain.

In the electromagnetic spectrum, what type of EM wave would have a 8y2wppk+ 2doswavelength of+ w2s8 pkopdy2 $10^3km$ 1 km? 1 m? 1 cm? 1 mm? $1\mu m$

Can radio waves have the same frequencies a m o6/kq;2e udrb0qs ny1+jpu ,jn2v(rs sound waves (20 Hz–20,000 Hz)?

Can two radio or TV stations broadcast on the same carrier frequency?gum 2t 7jki: hwx4x7/ h57ksbr Explain.

If a radio transmitter has a vertical antenna, should a receivsl z1z.:48d7sjyiho ier’s antenna (rod type) be vertical or horizontal jy4d. 1lso: i szh87zito obtain best reception?

The carrier frequencies of FM broadcasts are much higher than for AM broadf2nl m)z qzz-; )g-1 bg.qnebwcasts. On the basis of what you learned about diffraction in Chapter 11, explain whybqn)mzwqnbg z-z1 2-g;l)e f. AM signals can be detected more readily than FM signals behind low hills or buildings.

Discuss how cordless telephones make use of :k7hz8v 1zd 0;xnvqcu EM waves. What about cell phones?

A lost person may signal by flashing a flashlight on and off usiakdtw4vmt. ;7ng Morse code. This is actually a modulated EM wave. Is it AM or FM? What is the frequency of the carrier, approxim7dv.tkt 4w;a mately?

  At a given instant, a 1.8-A current flows inxh y2qw3l.;p+q8z( daupw 5ua the wires connected to a parallel-plate capacitor. What is the rate at which the electric field is changing between the plate.(xpzpy dw583qulwa 2 +huaq;s if the square plates are 1.60 $cm$ on a side?    $\times10^{14}\mathrm{V/m}\,\cdot \mathrm{s}$

  A 1200$-nF$ capacitor with circular parallel plates 2.0 $cm$ in diameter is accumulating charge at the rate of 35 $mC/s$ at some instant in time. What will be the magnitude of the induced magnetic field 10.0 $cm$ radially outward from the center of the plates?    $\times10^{-8}\mathrm{~T}$
What will be the magnitude of the field after the capacitor is fully charged?   

  If the magnetic field in a traveli 0/jbqiu0do)c ng EM wave has a peak magnitude of 17.5 $nT$ at a given point, what is the peak magnitude of the electric field?    V/m

  In an EM wave traveling west, the B field osci4ltv k*d mbrhr1* g.k1llates vertically and has a frequenc4k1b.mr *lt 1g*khvdry of 80.0 $kHz$ and an rms strength of $6.75\times10^{-9}\mathrm{~T}$. What are the frequency and rms strength of the electric field, and what is its direction? (Fig. Below)
frequency    kHz
$E_{rms}$ =    V/m
direction  ----待选择----horizontal north-south linehorizontal south-north line 

  What is the frequency of a uj *tja8*anv9 f2j:fvmicrowave whose wavelength is 1.60 $cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelength of*ivm(zx b8)8- u 2fl:lghkls4q9 ebwfob-w+ m a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has frequeng w;y wcef9md-g: a-zt dr/4)rcy $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a wavelength of 6ko:7 pdb+x5y l 7f.pncjm-b b)50 $nm$. What is its frequency, and how would we classify it?    $ \times10^{14}\mathrm{Hz}$  ----待选择----visibleinvisible 

  How long does it take light to ei1ife;yl -jap z9c h; b-zw;j -f7a+yreach us from the Sun, $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-wave” radio broadcast band is referred to as7 eik - lydfg*8,hvumg +(kvt9 the 49-m band. What ihu+*-kl vdfv (y97tm8e kgg,is the frequency of a 49-m radio signal?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (other than the Sun)w hqi 20 4.p9+aggbsxu is 4.2 light-years away. That is, it takes 4.2 years for the light it emits to reach Earth. ai bsgp90hg+w2q.x u4How far away is it in meters?    $\times10^{16}\mathrm{m}$

  A light-year is a measure of distance (not th0 +pl c2*0l e lgcbvm8q/oz:pime). How many meters does light travel in a y0hpbvel 8cql*pgo0m cz/l+ :2ear?    $ \times10^{15}\mathrm{m}$

  How long would it take a message sent as radio waves from Eaj s0fp)qu.yj2i+o0nlk v a6( krth to reach Mars
(a) when nearest Earth,    s
(b) when farthest from Earth?    s

  A student wants to scale down Michelson’s light-speed experimi m zkhtt)4 *mzu7.vk2 x/lt)aent to a size that will fit in one room.)ak.m/ix)h tzvmt t*2 zk u74l A six-sided mirror is available, and the stationary mirror can be mounted 12 m from the rotating mirror. If the arrangement is otherwise as shown in (Fig. Below), at what minimum rate must the mirror rotate?    $\times10^6\text{ revolutions/s}$

  Who will hear the voice of a singer first — a person in the balcony 50.0 l2e+ m /bxs4jkm away from the stage (Fig. Below)/bes2l 4 mk+jx, or a person 3000 $km$ away at home whose ear is next to the radio? How much sooner? Assume that the microphone is a few centimeters from the singer and the temperature is 20$^{\circ}\,C$.
 ----待选择----away from the stage3000 km away at home  
   s

  Pulsed lasers used in science and med+40c ;fkattw8of xe*kicine produce very short bursts of electromagnetic energy. If the laser light 0f;+eotaft* xkk w 4c8wavelength is 1062 $nm$ (this corresponds to a Neodymium-YAG laser), and the pulse lasts for 32 picoseconds, how many wavelengths are found within the laser pulse? How short would the pulse need to be to fit only one wavelength?
N =    wavelengths
$\Delta t'$ =    fs

  The $\vec E$ field in an EM wave in free space has a peak of $21.8mV/m.$ What is the average rate at which this wave carries energy across unit area per unit time?    $\times10^{-7}\mathrm{~W/m^2}$

  The magnetic field in a traveling EM wave has an rms strength ofgje)g,z+;u -r 7joqn vi :tw8l;ap,lr 28.5$nT$. How long does it take to deliver 235 J of energy to $1.00cm^2$ of a wall that it hits perpendicularly?    days

  How much energy is tran g/f/ k .uj*pn6gxs4ivsported across a $1.00-cm^2$ area per hour by an EM wave whose E field has an rms strength of $38.6mV/m?$    $\times10^{-6}\mathrm{J/h}$

  A spherically spreading EM wave comes from a 1200-W source. At a distance o /u nc*1y;1ca4 )dcoufppvy0p f 10.0 m, what is the average intensi4oa0/duy11fuppv*c;cp c )ny ty, and what is the rms value of the electric field?
S =    W/$m^2$
$E_{rms}$ =    V/m

  A 12.8-$mW$ laser puts out a narrow beam 1.75 mm in diameter. What are the average ($rms$) values of E and B in the beam?
$E_{rms}$    $\times10^3\,\mathrm{V/m}$
$B_{rms}$   $\times10^{-6}\,\mathrm{T}$

  Estimate the average power output of the Sun, gb -u :g8jz1wrriven that about $1350\mathrm{~W/m^2}$ reaches the upper atmosphere of the Earth.    $ \times10^{26}\,\mathrm{W}$

  If the amplitude of the B field of an EM w1fo go1fcvw kcd/f n( p3;k7,zave is $2.5\times10^{-7}\mathrm{~Т},$
(a) what is the amplitude of the E field?    V/m
(b) What is the average power per unit area of the EM wave? $\overline{I}$ =    $W/m^2$

  A high-energy pulsed laser emits a 1.0-ns-hbe. m,ndpfi;n+bg :1v q/h y-long pulse of average power $2.8\times10^{11}\mathrm{~W}.$ The beam is $2.2\times10^{-3}\mathrm{~m}$ in radius. Determine
(a) the energy delivered in each pulse,    J
(b) the rms value of the electric field. $E_{rms}$    $\times10^9\mathrm{V/m}$

  Estimate the radiation pr-;jk, t jxy h pg734n7z5(k k,nvlhv5g7ykveyessure due to a 100-W bulb at a distance of 8.0 $cm$ from the center of the bulb. Estimate the force exerted on your fingertip if you place it at this point.
P =    $\times10^{-6}\mathrm{N/m^2}$
F =    $\times10^{-10}\mathrm{N}$

  What is the range oflay1rdyt,0k) wavelengths for
(a) FM radio (88 $MHz$ to 108 $MHz$)    m to    m
(b) AM radio (535 $kHz$ to 1700 $kHz$)?    m to    m

  Estimate the wavelength for 1.9-GHz cell phone rzm s889+ fmxu.t)bdx aeception.    m

  Compare 940 on the AM dial to 94 zzjvkupl+a9+ l/ f +5uon the FM dial. Which has the longer wavelength, and by what factor is it lar+ k+/9jlzual+u5zvfpger?
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths for two TV chn 3h+2r srgi3ab+s( :isxo6n*3k kexpannels that broadcast at 54.0 MHz (Channel 2) and 806 MHz :ina 3gon(6+ h3r2s xkb*iekrx s3+ps(Channel 69)?
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in the tuner of an AM radioz4 rfmqiu21cfua*5a 6 has a capacitance of 2800 $pF$ when the radio is tuned to a station at 550 $kHz$. What must the capacitance be for a station near the other end of the dial, 1610 kHz?    $pF$

  The oscillator of a w 6iou(/3dg 0 popgne/96.1-$MHz$ FM station has an inductance of $1.8\mathrm{~}\mu\mathrm{H}.$ What value must the capacitance be?    $pF$

  A certain FM radio tuning circuix 7s0q. jbdp.vt has a fixed capacitor $C=840\mathrm{~pF}.$ Tuning is done by a variable inductance. What range of values must the inductance have to tune stations from 88 $MHz$ to 108 $MHz$?    $nH$ $\leq$ L $\leq$    $nH$

  An amateur radio operator wishes to build a w 4tw1 66z8idwh-/;ckdumuww receiver that can tune a range from -4kwu 8iz6w;mc w1dutw 6/hw d14.0 $MHz$ to 15.0 $MHz$. A variable capacitor has a minimum capacitance of 82 pF.
(a) What is the required value of the inductance?    $\mu H$
(b) What is the maximum capacitance used on the variable capacitor?    $pF$

  A satellite beams microwave radiation with a power of 10 1pg1hk+ u9txnqes2b7 $kW$ toward the Earth’s surface, 550 $km$ away. When the beam strikes Earth, its circular diameter is about 1500 m. Find the rms electric field strength of the beam.    $V/m$

  A 1.60-m-long FM antenna is oriented parallel to the u+/0g h)u k zfb8rr(tzelectric field of an EM wave. How large must the eleckrbf)ug rut(0 /zh+8ztric field be to produce a 1.00$-mV (rms)$ voltage between the ends of the antenna? What is the rate of energy transport per square meter?
$E_{rms}$ =    $\times10^{-4}\mathrm{V/m}$
S =    $\times10^{-9}\mathrm{V/m^2}$

  If the Sun were to disappeag 3lli96ohwg8r or somehow radically change its output, how long would it take for us on Ehglil8go 6 39warth to learn about it?    min

  Light is emitted from an dt)8 b pvfb 4kgsi) 4jyw:e-d6ordinary lightbulb filament in wave-train bursts about b w6edy4)pvdb s- if:kt 48j)g$10^{-8}\mathrm{~s}$ in duration. What is the length in space of such wave trains?    m

  (a) How long did it take for a message sent from Earth tf :qs md c6j/p0w4my-i 1rps7uo reach the first astronauts on th:qpmd10fuws-s4i jc6/ mr7yp e Moon?    s
(b) How long will it take for a message from Earth to reach the first astronauts who arrive on Mars; assume Mars is at its closest approach to Earth $(78\times10^6\mathrm{~km})?$   min

  A radio voice signal from the Apollo crew ola,2 xp(oai- cto6*s2 pz3vrr n the Moon (Fig. Below) was beamed to a listening cr p2sr*c ztv2(lxo3p or, 6a-aiowd from a radio speaker. If you were standing 25 m from the loudspeaker, what was the total time lag between when you heard the sound and when the sound left the Moon?    s

  Cosmic microwave background radiation fills all space eu(h zw1 51iajwith an average energy densityj 1 1u5ze(aiwh of $4\times10^{-14}\,\mathrm{~J/m}^3.$
(a) Find the rms value of the electric field associated with this radiation.    $V/m$
(b) How far from a 10-kW radio transmitter emitting uniformly in all directions would you find a comparable value?    $km$

  What are $E_0$ and $B_0$ 2.00 m from a 95-W light source? Assume the bulb emits radiation of a single frequency uniformly in all directions.
$E_0$ =    V/m
$B_0$ =    $\times10^{-7}\mathrm{T}$

  Estimate the rms electric fieldlgkevj - o9+. n;vk9vs in the sunlight that hits Mars, knowing that the Earth receivnve9+- v.9j l;sogvkk es about $1350\mathrm{~W/m^2}$ and that Mars is 1.52 times farther from the Sun (on average) than is the Earth.    $V/m$

  At a given instant in time, a traveling EM wave6d.i:(xai-r5-ys v wz;7j itulyjh 0l is noted to have its maximum magneti.jy 0 i6dya7ri sjutlvz 5:wl-(-h ;xic field pointing west and its maximum electric field pointing south. In which direction is the wave traveling? If the rate of energy flow is $560\mathrm{~W/m^2}$ what are the maximum values for the two fields?
 ----待选择----downwardupward 
$E_0$ =    $V/m$
$B_0$ =    $\times10^{-6}\mathrm{T}$

  Estimate how long an AM antenna would have to be jt 0/:p) ifwgcif it were
(a) $\frac{1}{2}\lambda$    $m$
(b) $ \frac{1}{4}\lambda$ AM radio is roughly 1 $MHz$ (530 $kHz$ to 1.7 $MHz$).    m

  How large an emf (rms) will be generated in an antenna that consists of a 3 a-r:hbo -r6zz;zgt t+80-loop circular coil of wt ;z:r-gzr6b+aoh zt-ire 2.2 $cm$ in diameter if the EM wave has a frequency of 810 $kHz$ and is transporting energy at an average rate of $1.0\times10^{-4}\mathrm{~W/m^2}$ at the antenna? [Hint: You can use Eq. 21–5 for a generator, since it could be applied to an observer moving with the coil so that the magnetic field is oscillating with the frequency $f=\omega/2\pi$]    $mV$

  The average intensity of a particular+9ghcn9k-5oi 1 hxvzc1cu 1xs TV station’s signal is $1.0\times10^{-13}\mathrm{~W/m^2}$ when it arrives at a 33-cm-diameter satellite TV antenna.
(a) Calculate the total energy received by the antenna during 6.0 hours of viewing this station’s programs. U =    $\times10^{-10}\mathrm{J}$
(b) What are the amplitudes of the E and B fields of the EM wave?
$E_0$ =    $\times10^{-6}$ $V/m$
$B_0$ =    $\times10^{-14}$ T

  15 km from a radio station’s transmitting antenna*sbcc;fl6m3i 7,h/a(do 9hwgk-l a 33hf fylv, the amplitude of the electric field f7 y3as3 c*kl ahhm h(bgf,vi936dwl;fol-/cis $0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitance of a radio tuner consists of six plates connected toge7v(k d)(r)(bijni qhgyua ;w z(st,x/theth,)r(/wsivaz u ( gby)(jn7qdi;k (x r placed alternately between six other plates, also connected together (Fig. Below). Each plate is separated from its neighbor by 1.1 $mm$ of air. One set of plates can move so that the area of overlap varies from $1.0cm^2$ to $9.0cm^2$.
(a) Are these capacitors connected in series or in parallel?  ----待选择---- seriesparallel 
(b) Determine the range of capacitance values.    $pF$ $\leq$ C $\leq$    $pF$
(c) What value of inductor is needed if the radio is to tune AM stations from 550 $kHz$ to 1600 $kHz$?    $mH$ $\leq$ C $\leq$    $mH$

  A radio station is allowed to a,r4i i ecshlov 6-1h)rtx88abroadcast at an average power not to exceed 25 $kW$. If an electric field amplitude of is considered to be acceptable for receiving the radio transmission, estimate how many kilometers away you might be able to hear this station.    $km$

A point source emits light energy uniformly in all directions aemt*bmx,mtpv.r4-g g t9h 1z1t an average rate - gt1,mgt *mrv9e.x zp41mtbh$P_0$ with a single frequency f. Show that the peak electric field in the wave is given by
$E_0=\sqrt{\frac{\mu_0cP_0}{2\pi r^2}}.$

  Suppose a 50-kW radio station emit uzf:ftefmw4td:pou t 3(f,.:k 7.jrns EM waves uniformly in all directions.
(a) How much energy per second crosses a $ 1.0-m^2$ area 100 m from the transmitting antenna?    W
(b) What is the rms magnitude of the $\vec E$ field at this point, assuming the station is operating at full power?    $V/m$
(c) What is the voltage induced in a 1.0-m-long vertical car antenna at this distance?    V

  Repeat Problem 65 for a distance of 1e*e ;y 0t ime(7sk(t a2wponl200 km from the station.
(a)    $\mu W$
(b)    V/m
(c)    V

  What is the maximum power level of the radirp4e u/,anoal+z/8:6ou aujmg n 9lpx ,rd9u+ o station of Problem 52 so as to avoid electrical breakdown of air at a distance of 1.0 m from the antenna? Assume the antenna is a point source. Air breaks down in an eln/mj 8ul+a:n rgp aa9,uo/46uxe+d p ro9l ,zuectric field of about $3\times10^6\mathrm{~V/m}.$ [Hint: See Problem 51.]    $\times10^{11}\mathrm{W}$