The electric field in an EM wave traveling north oscillates in an east–wes/66titkuaep3 xkmcr j.3wo8 1 t plane.6ttok/rmj 1k8cxpi a.u36w3 e Describe the direction of the magnetic field vector in this wave.

Is sound an electromagne yk; 9w4vj*rdnq9;pts3 pi :/5erknd aykox68tic wave? If not, what kind of wave is it?

Can EM waves travel through a perfect vacuum? Cela:3;p8g zw6gjq41vhuh4ki an sound waves?

When you flip a light switch on, does )l 5zgl l1 dm,wiz2--ixetcu-the light go on immediately? Explain.

Are the wavelengths of radio and television sirjl kq4+6o1q-vfr q*m gnals longer or shorter than those detectable fo q+ kvr4-6rjm*1lqqby the human eye?

When you connect two lypk: 60od8izxoudspeakers to the output of a stereo amplifier, should you be sure the lead-in wires are equal in 6x8yi :kzd0polength so that there will not be a time lag between speakers? Explain.

In the electromagnetic spectrum, what type of EM wave woul*ulgacwpy71bf6: wf (d have a wavelength offugc1lpy:(7 bwaf*6w $10^3km$ 1 km? 1 m? 1 cm? 1 mm? $1\mu m$

Can radio waves have the sab-b i6+,wv oaqme frequencies as sound waves (20 Hz–20,000 Hz)?

Can two radio or TV stations broadcast on the same carrier frequenca(q+ s: lxav4vy? Explain.

If a radio transmitter has a vertical antenna, should a receiver’s anten66opped(6x y 9ocoqv5na (rod type) be vertical oypoo(6xo 6cpev65q d9 r horizontal to obtain best reception?

The carrier frequencies of FM broadcasts are mu zesj f:)z/:qlch higher than for AM broadcasts. On the basis of what qzs:/e: f)zljyou learned about diffraction in Chapter 11, explain 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. ( ,5kcnd6wdbrWhat about cell phones?

A lost person may signal by flashing a flashlight on zskw bi+ 2pwz(bw;0*yls4 8uwand off using Morse code. This is a4zs+wp 8b2wlyu; iw(wb* s0z kctually a modulated EM wave. Is it AM or FM? What is the frequency of the carrier, approximately?

  At a given instant, a 1.8-A vylknxo0*49 u78q dd3ax5 nnccurrent flows in the wires connected to a parallel-plate capacitor. What is the rate at which the electric field is changing between the plates if thq9 nd* lc5x47un3yvnk8xdoa0e 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 travelin6d0.nz*t+mfe 3msdn b h f84vxg 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,e w;xtq ts6r0;r4wc9jm qx0)s the B field oscillates vertically and has a frequensw w4m tx06j qs9trrxe);q0 c;cy 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 au dki nc8cxw:h) b)e8) microwave whose wavelength is 1.60 $cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelengthe.jfw(5h 7/y;a;nxriec p1il7n wz 8 h of a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has frequjd7sxjj(sm /3)2 jeavency $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a wavelength of c4sv0:m6d6xhcj .c dhlp.bn6 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 lig. y- z-ap(knl5bo e9q(pzvo -vht to reach us from the Sun, $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-wave” radio broadcast bmpw8 ) o-jb m ;zvrw/z3w)xrh9and is referred to as the 49-m band. What is the frequency om))ww;p/rzm8 v bx3ozwh9j r-f a 49-m radio signal?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (othz w *v:n(d5kmg e6u zio49u3bxer than the Sun) is 4.2 light-years away. That is, it takes 4.2 years for the light 45okgv(9uuz63bz inxd:*e w mit 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).nxn/obcvplc;(+g3*/ gxb l, u How many meters does light tra/n u xg3lpgl obc/*v,c; nxb(+vel in a year?    $ \times10^{15}\mathrm{m}$

  How long would it take a message sent as radio waves from Earmpb8n3fb -dn* th to reach Mars
(a) when nearest Earth,    s
(b) when farthest from Earth?    s

  A student wants to scale down Michelso3tn5x3xd;ylb uvp iek+o 4,( gn’s light-speed experiment to a size that will fit in one room. A six-kg3n+e ixvl(53tuy x4bdop,;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 voicj0qgfyf oz+2t*x dy3/ e of a singer first — a person in the balcony 50.0 m away from the stage (Fig. Below), o+t 0z godyyfx/3j* 2qfr 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 medicin0t;tk bk+knnv jf1-.7 ty:)w jyp fg.ge produce very short bursts of electromagnetic energy. If the laser light wavelength is 1062 gyt gn0+-1fkj bj n)f7wy;k.k.p ttv:$nm$ (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 vdt*vd 0p e-;*t io,djan 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 tvzprg;416 w4ydm1o rf ransported 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 60v c,/u clj5vlef(uc bo;53tnavk2x 1200-W source. At a distance of 10.0 m, what is the average intensity, and what is the rms value of the electric 2j nv 5fbx6teuc3c/clla;0 o5(vku v, 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 powev knz9xq(2ie 0r 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 ism,(og1lq(ph h m.fl2y $2.5\times10^{-7}\mathrm{~Т},$
(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 a r9e-x4 vi;aeaverage 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 du*q4bu del:xj9gj:3bt* sq )bqe 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 yd);f)lans ml 7n1mw;au*h9f
(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 reyejg1z0 -njf 6ception.    m

  Compare 940 on the AM dial to 94 on the FM dial. Which has the longer wavexf5,f*, mo xsyiv ah7d45 tn/ilength, and oam5fyxt n4xvfs5/* ii h d,7,by what factor is it larger?
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths for two TV c( w3 7s;mpsbymhannels that broadcast at 54.0 MHz (Channel 2) and 806 MHz (Channel3m(bsypsm7 ;w 69)?
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in the tununs9ej, r1p9sncgvhr2;nt5(l nnq: 0 er 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 96.1masl td13sid pjr;3 /8-$MHz$ 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 fixevw+79ehy9hb yiq y4- ld 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 tunetu norgbz3+vz9; dwn),f yk 74 a range from 14.0 z+ y3rnu; wvnf9t4)d,kzbo g7 $MHz$ 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 microw3xx-8 h ft3+p5s 3lx--bj3bxj ntqdimave radiation 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 parallepkeh qj z8s6yv)d .m.bvb-i//l to the electric field of an EM wav) .hev qis /m-z /k.vy86bpbdje. How 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 rajx(e wc.r rf x2;bi 7euuah4a3;,lp j)dically change its output, how long would jia;3j;74 refeub(wpx, xhuc) lar2. it take for us on Earth to learn about it?    min

  Light is emitted from an ordinary lightbulb filament in wave-train bur7((.kw *fwl-ucis ueez) a:ctsts about kacwu.7):u*tlzs( e-wfe ic ($10^{-8}\mathrm{~s}$ in duration. What is the length in space of such wave trains?    m

  (a) How long did it take fobd:3lh)2me p4n 5xs wqlc,7p dr a message sent from Earth to reach the first astronauts on the Moon?)h:3sn2m,7llb 5e xc4pdqwp d    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)t1 sp.mk4ws2wnn;ynt q9bt0 7 was beamed to a listening crowd from a radios14btw tqn02nspn 9 k .ym7w;t 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 backta,tct(9/y0 a6th vi tground radiation fills all space with an average energy dens y6taa(hc/9ivt t ,0ttity 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 sunlj(xfmrqv+8tc r.lq(l0 ,.xuk ight that hits Mars, knowing that the Earth r(8jq m0( r. x vcflqrltk,.xu+eceives 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 r(n, fwf+(f *eznyhl- noted to have its maximum magnetic field pointing west and its maximum electric field pointing south. In which directionf+n(hzyf f-w(,r enl* 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 i;o*okcmfe )o9,s(5wfq 28x(r rvura ef 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 cpq dz7:am0zf s4z9cl(onsists of a 380-loop cizm(4 7 :fz zcplds90qarcular 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 (iaksp/ dj 9 47c4flyea 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 station’s transmitting antenna, the y09y9u*yt9mx nch4 mm0kqj + oamplitude of the electric field is y hnxk *yq04mm y 9ct+9u90jom$0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitance of a radio tuner consisr4as3s -3cotl: xr1o bts of six plates connected together placed alternately between six other plates, also connected together (Fig. Below). arsl:ctx3 obs-r o1 43Each 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 broadcaz3huy0 c 9co ag72nhlrf4u9w2st 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 unifrjqbjbl5xck9 +6 3p g9ormly in all directions at an average rate 5xl+6c 9q9bj gp3jkbr$P_0$ 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 emitgg1+/erot:n r wo:)w; z9gmecs 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 stavrifk,0j ;2ohysn2:c(wmhx 0tion.
(a)    $\mu W$
(b)    V/m
(c)    V

  What is the maximum power level of the radio0l73urfu* r;3zf fxpm station of Problem 52 so as to avoid electrical breakdown of air at a distance of 1.0 m from the antenna? Asurp;r7fz 3fu*0xm l 3fsume 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.]    $\times10^{11}\mathrm{W}$