The electric field in an EM wave traveling north oscillates in an east–west pla6/jvr2 ixuww-ne. Describe the direction of the magniw xv26/wuj -retic field vector in this wave.

Is sound an electromagnetic wa hgva :6xr4rcr-pux+/3,kz ; tl )yznnve? If not, what kind of wave is it?

Can EM waves travel through a perfect vacuum? Can sihkf jkx62 bzqwg1 )09ound waves?

When you flip a light switch on, does the light go on immediatdd5 s*;ew ph1nely? Explain.

Are the wavelengths of radio and tel9iqy+wlvj04 6a0 uj vn2/ 3kps5 lurmgevision signals longer or shorter than those detectawlarju0sql0j 6 45 3 9k/vnmvu2ig+ypble by the human eye?

When you connect two loudspeakers to the output of a stereo amplifier, should ywjoj a3j9n :ud9zeg-6ou be sure the lead-in wires are equal in length so that there will3ue:dw6 gj jja9 z9-on not be a time lag between speakers? Explain.

In the electromagnetic spectrum, what type of EM wave would have a wavelen 6fcaa6;k1verdj1di74cnrb 2 gth of2kde1ajfv cr4iad ;76 6nbc1 r $10^3km$ 1 km? 1 m? 1 cm? 1 mm? $1\mu m$

Can radio waves have ai xm ;h(vo lxe2ovi-1 m(:(guthe same frequencies as sound waves (20 Hz–20,000 Hz)?

Can two radio or TV stations broadcas vwxpjj2;lzz) b.wm i-uw.)dh93wmrep-;wl1t on the same carrier frequency? Explain.

If a radio transmitter has a vertical antenna, should a receiver’df3 .b03sgry-2exdm v 2k oum/s antenna (rod type) be vertical or b.ko2s /myrfedd-vumx 3230g horizontal to obtain best reception?

The carrier frequencies of FM broadcasts w0vfj5i9 agjn ,gip b/ut(-(fare much higher 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 signals behind low hilj f/ 9guv,i(jitg( 0nb5p w-afls or buildings.

Discuss how cordless telephones make use of Exjqxzqp/l 0hg1 :b f)9v f5,miM waves. What about cell phones?

A lost person may signal by flashing a flashlight on and off oat(77egdx 7,i 0g0mnj9v wrf using Morse code. This is actually a modulated EM wave. Is it AM or FM? What is the freq,007 vj 7dwg g(emrn 7itax9fouency of the carrier, approximately?

  At a given instant, a 1oig h0* bqon:hg0t )6 :m ,h19slderwaxa8k3c.8-A current flows in the wires connected to a parallel-plate capacitor. What is the rate at which the electric fieldl 3,dohc1swgm6)xin 9h:ka8abg* 0rt0q e:oh 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 traveling4ai1ou*jim2;b n5 wsp 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 oscillates vvapjx xg:iv.+ b* xrohta /5,a;*a*blertically and has a frequency o : bjvt +,vr a;a*ahxo *ix*lpgx5a/b.f 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 microwave w e5g;:gvchz9kcgvlg /5j -+2 +zi wnld d4d1hxhose wavelength is 1.60 $cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelength -n*( 0 0qkjmkek 2e5 1+ wst3lnhkvdtnof a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has frequencp9g( uvxq6 9vnw48 2msksv ;wsy $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a wavelengtho1dl43x m i)5i(zo jb3*g tmaf 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 qi m66(,jenx ous from the Sun, $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-wave” radio broadcast band is referred to h hpdddk9l)k;2q 9rb8 as the 49-m band. What is the frequency of a2lhk 9dpb ;kd)rd 98qh 49-m radio signal?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (other than the Sun) is 4.2 lig6 3:h:wivjwrsje hi.( ht-years away. That is, it takes 4.2 years for the light it emits to reach Earth. How fars(iiv6eh:jr wj . h:w3 away is it in meters?    $\times10^{16}\mathrm{m}$

  A light-year is a measure of disp0ua;a u gh*- oyvl3c.tance (not time). How many meters does light travel i0luy 3up; haog.a*-vc n a year?    $ \times10^{15}\mathrm{m}$

  How long would it take a message sent as radio waves7wu. 0plfub lxwt0( w8 from Earth to reach Mars
(a) when nearest Earth,    s
(b) when farthest from Earth?    s

  A student wants to scale downo mv6du 1m/ot( 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 arrangement is otherwi dt ouvom1(m/6se 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 /vif::f akq4mp npo7 ;50.0 m away from the stage (Fig. Belowv/7;a4 f:p:fimko qnp ), 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 medicine produce very short bursts of electru*.yb4 xr z)v.*eviqpk md9d/ omagnetic enerpdkz)d** v.m/yr 9bux 4v.ieqgy. 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 traveling EM wave has an rmsifl u9pw+ b(h3vd.un u+1hc3k 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 acrosspv1paan4l55o f0tp+6gtq/a c 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 distai cb ubuj f9(yt,o/l7c1o. :zmnce of 10.0 m, what is the average intensity, and what is the rms value of the electric field? z c1 fj(uboc:m7u/lb,oi.y9t
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 pown:io9natb o( 9er 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 the B field of an EM wave ig8e(ic gkjak;0n; c 0l+; odqqs $2.5\times10^{-7}\mathrm{~Т},$
(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 ep3)re9xojx )kf amx:5 mits a 1.0-ns-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 pressure due to a 1zdpxtfs79i hn12v tkspqg0 (1uwq.*xaz17h- 00-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 wavelength9e4ckala c( f5s 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 receptiow97hr4,*)cr;k doddl,l 9jkmlqz lg7 n.    m

  Compare 940 on the AM dial to 94 on the FM dial. Which has the loti-ze 9mmn :q(nger wavelength, and by what factor m i: m(qz-t9neis it larger?
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths for twe 5: lk z u9imbvi3f*8x-m1uino TV channels that broadcast at 54.0 MHz (Channel 2) and 806 MHz (Channel 69)un 3 zimklv5:8 1mi bfeiux*9-?
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in the tuner r ne:+gxn9 h-tof 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 96.1-a0 2r+dn33k4 hh:ceizl9- lkl vlxeo4$MHz$ FM station has an inductance of $1.8\mathrm{~}\mu\mathrm{H}.$ What value must the capacitance be?    $pF$

  A certain FM radio tuning cir2laud*g1 s 0ulcuit 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 opepq/ viu/gosoh8rg3 1u;.)l 9yg8f ghd rator wishes to build a receiver that can tune a range from )/8;udyuq89o phggvhs/iog l1r3 .fg14.0 $MHz$ 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 powerg0 9 pcr1qp6vweokh37 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 ori;zo 0v6mkvoys3 ly *y)ented parallel to the electric field of an EM wave. Howsmvy; *oy6 0)okyz v3l large 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 disappear or somehow radically change its outpucvm)n.r ed zj96c un0 zgu719gt, how long would it take for us on Earth to learn abou jv1rgd un9z 69cg7cnmez)u 0.t it?    min

  Light is emitted from an ordinary lightbulb filament in wave-train bt54s/ z eld3izursts about tlzse5 i3 /4zd$10^{-8}\mathrm{~s}$ 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 to bhz 78q j lfz-4dlx-0ureach the first astronauts ob 47lx u-l d0-hfzzjq8n the 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 on the Moon (Fig. Below) was beag*bw: qer+qp4 -m.mw xmed to a listening crowd from a radio speaker. If you were standing 25 m from the loudspeaker, what was the total time lag betwepm. 4emwq-rwgqx:b+ *en when you heard the sound and when the sound left the Moon?    s

  Cosmic microwave background radiation fills all space wis zb(x*a2an6c .ak )pa lq.z*dth an average energy densit)dsb*ka l6pqn(za2.z *a.axc y 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 field in the sunlight that hits Mars, knowing that tfr):kb f+;hh.7izaf ehe Eartr7f+k; z.a h: ib)fefhh 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 hav.ziypq: mqe5+e its maximum magnetic field pointing west and q.yemqpz i:+5 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 (t7ory w b97gg-ke2dzbe 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 bpjoc cj5:h59/l o.g pq,g wph;e generated in an antenna that consists of a 380-lo lgp5h /co9oq 5; .,wp:gpcjjhop circular 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 v05yd74(ezgzx, fci1g2( uf9+zo sqe 9nij sza particular 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 sth (r8 xv2i bg xg4qg+3cr,lr-nation’s transmitting antenna, the amplitude of the electricgqr hbv,84-gx lr ni cx2(3+gr field is $0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitance of a radio tuner consxtt i,odyu)j/77xs :kists of six plates connected together placed alternately between six other plates, also connected together (Fig. Below). Each plate is separated fr)st/i:xy oj7,7uxtkd om 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 alm7m ejirr7zp-de -(,vrh,k9 ulowed to broadcast 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 directioj*t8il0kuxj 8 ns at an average rate0x kiu 8tjlj*8 $P_0$ 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 st 4/btd dz8k+szation emits 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 100 km from the stgrm6r ;6k14-vxly qgk b78k sqation.
(a)    $\mu W$
(b)    V/m
(c)    V

  What is the maximum power level of the radio station of Problem 52 so as to avf mjid;1xidwmx fb2:dxz + .:)oid electrical breakdown of air at a distance of 1.0 m from the antenna? Assume the antenna is a point )xjwfdm+iixd f;2z .d 1:m: bxsource. Air breaks down in an electric field of about $3\times10^6\mathrm{~V/m}.$ [Hint: See Problem 51.]    $\times10^{11}\mathrm{W}$