The electric field in an EM wave travelingu/n3 9fyj,hehlak+xe w t)-c8 north oscillates in an east–west plane. Des+)hfkyecet j8n/ 3u, 9h-l axwcribe the direction of the magnetic field vector in this wave.

Is sound an electromagxi3woy)ed 7/dpm(2 zcnetic wave? If not, what kind of wave is it?

Can EM waves travel through a perfect vacuum? Can so5 pz62 hnhw.chund waves?

When you flip a light switch on, does the light go on immediately? Explaio4r( 8hr::qept8 ylz xn.

Are the wavelengths of radio and television signalf3jsdm.pn32espf+n v0p; nb+qx 1f- ds longer or shorter than those detectable by the human eyp0pq v-npsed.mn1+s32 f;+nffb 3xj d e?

When you connect two loudspeakers to the output of a stereo amplifier, should ybz7dbjo pja5 *f)dn89 ou be sure the lead-in wires are equal in len8dzp)bjf*5o9 da7b nj gth so that there will not be a time lag between speakers? Explain.

In the electromagnetic spectrum, what tyqj4 xeqi4k9y6x -v2djc*ie ;ope of EM wave would have a wavelength of e -oc2dixjevq* i 64;9jx4ykq$10^3km$ 1 km? 1 m? 1 cm? 1 mm? $1\mu m$

Can radio waves have the same frequencies as sound waves (20 Hz–20,000 Hzppzm+bq h:2x f.4 tzs4)?

Can two radio or TV stations broadcastmaasvjzmq x4 2 d13m;-9z-jk.to bt 4h on the same carrier frequency? Explain.

If a radio transmitter has a vertical antenna, shydhv1fpl+d 1n kyk;au(8s ;u s+ (dwq-ould a receiver’s antenna (rod type) be veyvuq;pu a-s ;1dn 1k(8ys+l+ fd(wdhkrtical or horizontal to obtain best reception?

The carrier frequencies of FM broadcasts are muchsps6fjpg42 bx2 v3 b/g higher than for AM broadcasts. On the basis of what you learned about diffraction in Chapter 11, explapbs v4xf/26 b3j ggs2pin why AM signals can be detected more readily than FM signals behind low hills or buildings.

Discuss how cordless telephones make use of EM waves. Whawyohj+7 w2:q0g: sbvu t about cell phones?

A lost person may signal by flashing a ;ndc9 tf-ul0e1wh 2ige- 0ssoflashlight on and off using Morse code. This is actually a modulated EM wave. Is it AM or FM? What is the frequency of the carrie2g;1ct9 -dul0 fh s-sie0wnoer, approximately?

  At a given instant, a 1.8-3;s8efh4ml r- yc jht*A current flows in the wires connected to a parallel-plat8 tsrefch 3;m-ly* 4jhe capacitor. What is the rate at which the electric field is changing between the plates 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 traveling EM f6 tz,q0,:6 e-vx e.dmo:fngucx: xn uwave 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 fielpdr:)vm- m6m; o 7butw94kkfzd oscillates vertically and has a frequency:uk7w vm-pz4)kom md9f;br 6t 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 micrg.m76qm bwf rob9 n xi3ishq3e8 6d5t.(2uiloowave whose wavelength is 1.60 $cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelength osge(fd8+ fh )ik-jo -cf a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has frequency u:c(e96ojzrvd5va lk fg;-e ) $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a waveleng4b:7rnypj 4sf th of 650 $nm$. 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 reach us from the S)6 qktz rd(z2run, $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-,rnf.z7*bmxg4 yzmw 6wave” radio broadcast band is referred to as the 49-m band. What is the frequencr67ng mzyfzxbm., *4wy of a 49-m radio signal?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (other than the Sun) is 4.2 lighswgernf 7 5h:10fscz a4uz9u5t-years away. That is, it takes 4.2 years for uc fhna17g9ez 0z54ws r:fs5u the light it emits to reach Earth. How far away is it in meters?    $\times10^{16}\mathrm{m}$

  A light-year is a measure of distance (not time). How many meters does light traud/ 1kf2* 3 e4cc5a8vmsexqfkvel in a year?51fe x3dsc 2 ckv4fk*m8e uqa/    $ \times10^{15}\mathrm{m}$

  How long would it tazb(u -xrebmhip 6+d2 +oy *ax 0dz,9bmke a message sent as radio waves from Earth to reach Mars
(a) when nearest Earth,    s
(b) when farthest from Earth?    s

  A student wants to scale down Michelson’s light-speed experic6; **w * kd-h a mw-fq+i,alwwpk;vxlment to a size that will fit in one room. A six-sided mirror is ava;w cqwi+m;k 6 ,a*v lpd ax*w*flwkh--ilable, 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 pt8u2,sji g3i berson in the balcony 50.0 m away from the stage (Fig. Below), or a person ti 3,2busijg 83000 $km$ 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 medici gh1u ghptpz;(76v c8ene produce very short bursts of electromagnete gpch ;8h 1pz(t7ug6vic energy. If the laser light wavelength 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 tr tyx13:f39l ,v0;nzlcad3jpc g 9pj puaveling EM wave has an rms strength of 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 transported acr trwed+ :eb0smql/;i 8ul- 6kf0nk. fmoss 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 12phx0x j)ej1;m 00-W source. At a distance of 10.0 m, what is the average intensity, and what is the rp1 ;mxxjje0)h ms 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 S dcbe +49re)youn, given that about $1350\mathrm{~W/m^2}$ reaches the upper atmosphere of the Earth.    $ \times10^{26}\,\mathrm{W}$

  If the amplitude of the B fieldp vx 5 ,mf6p5wusi6tczlj) vdcwe91.7 of an EM wave 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-long pulse of averar+0gga v2qa1d:b- kqy ge 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 radiatihla6*t+bh.*94:zli me ho ku son pressure 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 of wavelengths for rk+twf 2- wuao,+- 0gyuf7n wu
(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 1.9ss(-hfsv2o (p rzt:b0 pz nn9:-GHz cell phone reception.    m

  Compare 940 on the AM dial to 94 on the FM dial. Whichqrj o 0z2ji+oeq1 y0m. has the longer wavelength, andiyoqqomj zr2e +1j.0 0 by what factor is it larger?
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths for two TV channels that+:/zg vs. darmkvr:j0 broadcast at 54.0 MHz (Channel 2) and 8060+z:k/mr.jvr g :dvas MHz (Channel 69)?
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in t -b0r0:rbasakhe tuner of an AM radio 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 rb,;tk(ud9y6fc m ,u h96.1-$MHz$ FM station has an inductance of $1.8\mathrm{~}\mu\mathrm{H}.$ What value must the capacitance be?    $pF$

  A certain FM radio tuning circuit has alo 5 bu;pkp/0u 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 receiver that can/o)f-of:f1s*js/s v ziesr k7 tune a range from 14siveszo -f:jso) 17 *s// rkff.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 radix:h fpb32gm5 lation with a power of 10 $kW$ 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 elecd5 ofau)-znhqt .8 v+gtric field of an EM wave. How largd.5 fo8g)n-z q+uhvtae must the electric 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 disapp 2ve3 ga+cnexih8sc (t3cr63near or somehow radically change its output, how long would it take for us on Earx2s8eecc ( 3i+ tr3a6vcg3nhnth to learn about it?    min

  Light is emitted from an ordinary lightbulb s,w5b enkfcq( 0d44tmfilament in wave-train bursts about kf w(tsqc,0dm4 bne54$10^{-8}\mathrm{~s}$ in duration. What is the length in space of such wave trains?    m

  (a) How long did it take for a message sxzsh1.i oa*69zdqn)qa0 9nh7iuza/ khc)x7 t ent from Earth to reach the first astronauts on the Moh.aznki z ch7 iqxa)/s6a)1tx9nquh*d79oz 0on?    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 fr z+ sxe6w9ht5 :vpbrs8.)1+acxkg keb om the Apollo crew on the Moon (Fig. Below) was beamed to a listening crowd from a radio speaker. If you were standing 25 m from the loudspeaker, what vkksa:hp5 gb9c)e+ze wb + 8. ts6x1rxwas the total time lag between when you heard the sound and when the sound left the Moon?    s

  Cosmic microwave background radiatio4wus7y 6) abss i8xda7n fills all space with an average energy densaui) ss8w6 y7d a74bxsity 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 elect r2 x 6en/uylp7*r-xkqf3 z9 xt2nxwa5ric field in the sunlight that hits Mars, knowing that the Earth rece xktn*5r/ax2yq wpux9-xe nfrlz3 627ives 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 wave is noted to have s mydgb4 tn .omb7,wu e:9ng3/its maximum magnetic field pointing west and its maximum electric field pointing south. In which direction is the wave traveling? b:ngg/ .mw4b no,3esud9y 7 tmIf 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 w4m jtbo9o6rp;ould have to be if 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 i4h+ ltw*np8vp jy;c1uc.hz d 3n an antenna that consists of a 380-loop circularh8lc;v.*d14+uhzyn ct pwj3 p coil of wire 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 TV station’s sig .ikza0vw(17he3wl2 n zvx q.lnal 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 transmittinss 9.-vky frm:g antenna, the amplitude of the electric f-rks:vm .9fsyield is $0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitance of a radio tuner consisi8kikc),) +enl aka6fts of six plates connected together placed alternately between six other plates, also conneli)kk +ik 8e6cf, a)ancted 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 broadcast at a,l5fi3r h )wq 7zp2amtn 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 at an aver8+3) fx,2ezqn rer qj :7pyeenage rate,prjree)qe :q8 2e37n f nxzy+ $P_0$ 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 emits EM waves uniformly in all direh0uw rn)uk7lxkks 8 c8 y3j-5pctions.
(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 1y y .+vr:8hwbh00 km from the station.
(a)    $\mu W$
(b)    V/m
(c)    V

  What is the maximum power level of the radio station of Problem 52 ,h;0ctmq*)2 r sz uv.bk8ksbk so as to avoid electrical breakdown of air at a distance of 1.0 m from the antenna? Assume hk; *ukzrm.bvt0 ,sb8 s)kqc2the antenna is a point source. Air breaks down in an electric field of about $3\times10^6\mathrm{~V/m}.$ [Hint: See Problem 51.]    $\times10^{11}\mathrm{W}$