The electric field in an EM wave travelingaqb rtc,f*e 93 north oscillates in an east–west plane. Describe the direction of e, *r3at9cfb qthe magnetic field vector in this wave.

Is sound an electromagnetibi6* 9vuwj( reuc2 fz3c wave? If not, what kind of wave is it?

Can EM waves travel through a perfect vacuum? Can sound g1 q/(2gwrrxzwaves?

When you flip a light switch on, does the czu76 ub3pink8bm8s6 light go on immediately? Explain.

Are the wavelengths of radio and television signals lo(2ju29 30z) zqvv4ezgpg yon snger or shorter than those detectable by the h2ep 3q 0g2ugzyj z nov)zvs4(9uman eye?

When you connect two loudspeakers to the output of 6d 24ighbm:.gsq ei 7tm 0f,ika stereo amplifier, should you be sure the lead-in wires are equal in length so tha0qi 2g.7 fim:bdkgt mh46,siet there will not be a time lag between speakers? Explain.

In the electromagnetic spectrum, what type of EM wave would have a wavelv/6k y,qilms) ength of qvk lym si),/6$10^3km$ 1 km? 1 m? 1 cm? 1 mm? $1\mu m$

Can radio waves have the same frequencies as sound wasazud0*)c(m. nlihvh3 msv +(ves (20 Hz–20,000 Hz)?

Can two radio or TV stations broadcast on the same ldv6x*1 qwhyr cov6ec p,4;a4 9a(vxm;pte h2carrier frequency? Explain.

If a radio transmitter has a vertical antenna, shy -c h7 0dmhcr3hq(l(iould a receiver’s antenna (rod type) be vertical or horizo3h0-c ihd hl7(qcmr (yntal to obtain best reception?

The carrier frequencies of FM broadcasts are much highnwrd yssaa joku x 358to1vt0*oi9l0m *+s-8h er than for AM broadcasts. On the basis of what you learned about diffraction in Chapter 11, explain why AM signals can be detected more readily than FM signar5 t0k- t+8l s asjyvuiw109a *om*hxn8sodo3ls behind low hills or buildings.

Discuss how cordless telephones make use of EM waves. Wbo4f seoy77 5c-1v gvvhat about cell phones?

A lost person may signal by flashing a flashlight on and offi e0)6j .b80cl,e vz wpdos+el using Morse code. This is actually a modulated EM wave. Is it AM or FM? Whatdv0sie b,z.lj 60e)l8+ceo pw is the frequency of the carrier, approximately?

  At a given instant, a 1.8-A curren zlau3slcrcua ;) 4tla))*6zwt flows in the wires connected to a parallel-plate capacitol6*ac )z z4s)u urca wlt;a3l)r. 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 travelinkond-ef l m5r+p4:-kkh o. .djg 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 1az33e ebmo g-oscillates vertically and has a frequenc3age1-m ezo 3by 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 frequency1bc4 ilr yiuv;;9 nh/o of a microwave whose wavelength is 1.60 $cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelength ofvr goxd2*** 7tperhi 1z+w x2y a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has frequencyssa1,9s mq6jj 0 k c5fee66dnr $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a wavelength of 650oix -6b(6m mhd $nm$. 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 reas a3sf3wibpgims5 2. 7ch us from the Sun, $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-wave” radio broadcasbv/z psl5 )5k4wfhd;xt band is referred to as the 49-m band. What is the frequency of a 49-m radio signxpwd;4h/kz )s55bvl f al?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (other than the Sun) is 4.2 light-years conls:d t7 ug0m1ar-( away. That is, it takes 4.2 years for the light it emits to reach Earth. How far away is it in:7org1tcm 0l(sd- anu meters?    $\times10^{16}\mathrm{m}$

  A light-year is a measurcndlbbax4( 1 6i /6hjre of distance (not time). How many meters does light travel in a year?(6jcxbn6ilrb1 4h / ad    $ \times10^{15}\mathrm{m}$

  How long would it take a message sent as radio waves from Earth to reatvm oxz;l5d ,+,8smaxch Mars
(a) when nearest Earth,    s
(b) when farthest from Earth?    s

  A student wants to scarpbzgd9(+q qu mmn,6*le down Michelson’s light-speed experiment to a size that will fit in one room. A six-sided mirror is available, and the stationary mirror can be mounted 12 m from the rotating mirror. If the arrangemq p +u,g9nm b(dmz*qr6ent 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 m awa q+ue dxu)ad8k)p 3ka8y from the stage (Fig. Below), or uk)x3 u da +)8qapk8dea 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 medic1gvn:m wmbd6gs9x f+,ine produce very short bursts of electromagnetic energy. If the laser lxg m 1wv6ndgm9b, sf+:ight 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 traveling EM wave has an rms strength owbh br8 dp9z.7f 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 transpo+307 *ph dfaok.jsr: ofjwt-qrted 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 spreadi9nzi3u b5sfzi/2nb 0fng EM wave comes from a 1200-W source. At a distance of 10.0 m, what is the average intensity, and what is the z n9ii 3fusf05 /bz2bnrms 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 powh f)ghw8ey3s)c3m)x l qwmp( /er output of the Sun, given that about $1350\mathrm{~W/m^2}$ reaches the upper atmosphere of the Earth.    $ \times10^{26}\,\mathrm{W}$

  If the amplitude of v47rg e lph,h3;buo lcq 3cj:3the B field 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 gs iyvoxc .r75;8f; cwaverage 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 pressure due to zyksvtu1ebnp7 (:9)ba 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 ax+u2l*f ri, uv /qd-/uap14pq4ncpd
(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 forn0fzzi,y2o * (hkxir2 1.9-GHz cell phone reception.    m

  Compare 940 on the AM dial to 94 on the FM dial. Wh7 ok8;)pvlkt fich has the longer wavelength, and by wht7l)f k;kp 8voat factor is it larger?
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths for two Tn)7dipc4rg uvx+ 7(jwV channels that broadcast at 54.0 MHz (Channel 2) and 806 MHz (Channel 69)? (pr ij+4c7)7dun gvwx
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in the tunez hp4ff+617s s) 4.lcfhilwby r 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 9:z2k0h leyhlby r+7hi/(c 7sd 6.1-$MHz$ 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 a fixed capacitbpmuo.df3h)ldv* 0k 1 0a*mn kor $C=840\mathrm{~pF}.$ 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 buil1 ops ww/xixra0 0t,z2d a receiver that can tune a range from s twa,w/xi2x 0r1zop0 14.0 $MHz$ 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 42 k7kqc, dy9/ogetxa 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 tu4xxm50 ey: 0c2/kwj)w in cwzhe electric field of an EM wave. How large must the eleciwc/ w2)j 0zx0:mw5k4xy necutric 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 disappear or somehow rap z;rpx /bgnrj8x- 6j)dically change its output, how long wo 8r;xj-6 z/pjrg)bnxpuld it take for us on Earth to learn about it?    min

  Light is emitted from an ordinary)wbe.xu dc3ax9-8jcz9g wkm/ +qcjn* lightbulb filament in wave-train bursts about g 3dcmq)x8 .bwe/-acnx *wk9 +9jujcz$10^{-8}\mathrm{~s}$ in duration. What is the length in space of such wave trains?    m

  (a) How long did it taf(66m2niqb lgpt9x mo- vx055x iga4nke for a message sent from Earth to reach the first astronauts on the Moo0b562g gi pnm4avt xl9mo5fx(x6 iq-nn?    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 cre,c.uhj(z c5 mow on the Moon (Fig. Below) was beamed to a listening crowd from a radio speaker. If you were standing 25 m from the loudspeaker, wzc u5jmhc o.,(hat 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 with a c01u(gk4kkh jn average energy density ojh k40(g1u kkcf $4\times10^{-14}\,\mathrm{~J/m}^3.$
(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 field in the sunlight that hits Mars, knowi1y+8fq97w 7n2inemwe /na + pmymyrv*ng that the m 9 qy7fe ywn+enin8rm*v2aw + 1/p7ymEarth receives 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 hasrw k,* )+n1y*-/ n qtmzurjlmve its maximum magnetic field pointing west and its maximum electricknm1znu/yl*s*rmq jrt ,-w)+ 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 antenn kx-xhvuoi-99 a would 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 in an antenna that h;7l4qmzeno- i1ikedj-xh;lh sv3/* consists of a 380-loop circular coii* qv o;exhz13 n/ 7i4dhj lhl;--ksmel 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 TVc0 h( o9cb 1lf7ju5eus 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, the amplitude0qrhizqr)v m9,ex2k7 of the electric field is mk e7hq)i qv02 ,xr9rz$0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitance of a radio tuner consists of six plates co1ra-d *yx+-o x: tfqk. 7y mrz*7dqruonnected together placed alternately between six othr kro t.zm-xq77ox +u -q *yd1:dfy*arer 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 broadcast at an average power not to exceed 25k )yr mloy(l4 o9tcd/9 $kW$. 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 a1neom*q2 6 c/8:3m jzid,hwjqple j umj9.h 1lverage rate 89*2hqj ,mme3q.poh1j:cjl 6/ imjnd uezw1l$P_0$ 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 allt 64vj(r0cy oc 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 100 km from the statitc 2d r7n,5b7jz(e( yuctbq7con.
(a)    $\mu W$
(b)    V/m
(c)    V

  What is the maximum power level of the radio st1eitw8/ z iuvt132wlyation of Problem 52 so as to avoid el3zi 1lt1uywt2ivew8 /ectrical 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 electric field of about $3\times10^6\mathrm{~V/m}.$ [Hint: See Problem 51.]    $\times10^{11}\mathrm{W}$