The electric field in an EM wave traveling north oscillates in an east–jp w5*; j/ewexwest plane. Describe the direction of the magnetic field vector in thi wjwp5* jexe;/s wave.

Is sound an electromagnet2zmcuu-ie4ui eo37j /1a g 6f(vugwy*ic wave? If not, what kind of wave is it?

Can EM waves travel through a perfect vacuum? Can sound wa7id4o+m5n z a +fsjd3-enni +lves?

When you flip a light switch on,,u8 3,leev k)saf w)s4kvnm0g does the light go on immediately? Explain.

Are the wavelengths of radio and television signals longe)we g115fb+kw8 n2beytm tz s6r or shorter than those detectable by 2e8wtkmyzw)5+s 6fb gnb 11tethe human eye?

When you connect two loudspeakers to the output of a stereo amplifie8jh( (ls1qinm5k/ n5qfca-t4 e ou/fa r, should you be sure the lead-in wires are equal in lengl4 m //qaeqf5-ji akfno uctn ((18sh5th so that there will not be a time lag between speakers? Explain.

In the electromagnetic spectrum, what type of EM(wvu;f ,2xq0q-tsmhezr 8 +d 54yjrew wave would have a wavelength of (-s4 8jd tr5u+myfe; 02rwxhzw qv q,e$10^3km$ 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 Hz)c n3v.p p (2h +uvvmba8.op9xp?

Can two radio or TV stations broadcast on the same carrieret3 1w lw(/wjvo9eq1p hyra6- frequency? Explain.

If a radio transmitter has a vertical antenna, 54s*8y. 3flrg cy6; hjbij tpgshould a receiver’s antenna (rod type) be vertical or horizontal to obtain si r*fyp;tg .ylg5j 3b6j48 hcbest reception?

The carrier frequencies of FM bmps)/72djq ijroadcasts are 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 signaqj) p dsmij2/7ls behind low hills or buildings.

Discuss how cordless telephones make use of EM wavewaw u (+4r2 ,hgtfvh/ps. What about cell phones?

A lost person may signal by flashing a flashljvc cz+p;-f7oight on and off using Morse code. This is actually a ;oc7z-+pj vcf modulated EM wave. Is it AM or FM? What is the frequency of the carrier, approximately?

  At a given instant, a 1.8-A current flx/ycifh6 / 3ngk:daj n:k y.2lows in the wires connected to a parallel-plate capacitor. What is the rate at which the electric field is changing between the plate dn6.2hi3klcyy:/ /kagfn x:j 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 traveln2gn*m p vge -3a7y2xwing 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 fi:ypp * of-bcz3gf p7 rka/8af.eld oscillates vertically and has a frequency of 80p7p bag*:p/yro 8-f.acfk f z3.0 $kHz$ 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 whose wavelength is 1.604n tl+ua+wy 6c $cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelength of+4difbylj:)yqb eq;9 es8sj6 w3kv, l a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has frequency 1jywabzw8 m8r)a1wjryo50 v2 $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a wavelelijxc6p28 w9rm;po;pksw pn /9q 9 ,ehngth 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 kt37-.ilcetj a, oe 7sto reach us from the Sun, $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-wave” radio broadcast band is --mrff*pb41a xz 1z2jnk -rzlreferred to as the 49-m band. What is the freq 1z kxp4f1rznl--afzb*2 -jrmuency of a 49-m radio signal?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (other than the Sun) is 4.2 light-yebovj qq14: d)0p*qh)bw+rvlvl,p mj;ars away. That is, it takes 4.2 years for the light it emits to reach Earth. How far awa hp:p)0jvo 1qdv ,4;qb+llvmq*)wjbry is it in meters?    $\times10^{16}\mathrm{m}$

  A light-year is a measure of distance ((rd h0rto cqn (rc n3w*4bcg- 4/g:lmfnot time). How many meters does light travel i *r4f rglnm grw3c/c((tdn0h-q 4b: ocn a year?    $ \times10^{15}\mathrm{m}$

  How long would it take a message sent as radio)mxu 4gz7(f(xypkt n6 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 -oyp 2z qo;3t3 xw8twrexperiment 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 mirrrqy;z xt2 ww-3o3 o8ptor. 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 s kgtq4)/.a qaqinger first — a person in the balcony 50.0 m away from the stage (Fig. Bekqgtq) / a4aq.low), 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 bug.l 2kjeps1+f rsts of electromagn+ gfls1k.jp2 eetic 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 traveli+ocoal/ k 4b/ung 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 transpor.21al (hgn kctted 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.+ toys7yexavkc)0t he2i9q:k (. dn7c At a distance of 10.0 m, what is the average intensity, and what is the rms value of the elec7:h7k . deyyscvtqt e+n o0ac92)kx(itric 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 olj)bdi + +hsasz; z258tv ;jwpower 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 wa3jdu0fl(,8 7qsvpro2 , * zpvbqn syp+cv84z fve 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 g.gw6x6l+ o,gvvivqbj 7g5v1 ,tn-bepulse 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 t3rwil7 hf ga5f25j;fp4z4jbton2 w. no 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 forg/ w amwfie,9wx0ffn 4r3td96pj uj ctx3;-3e
(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-lw jv6, :ue2m(mtn*ce GHz cell phone reception.    m

  Compare 940 on the AM dial to 94 on the FM dial. Which has tha;4kg /wy5k celf:e+d e longer wavelength, and by what factor is it larg54dc+:ak yeew fg;/ lker?
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths for two TV channels that broadcast at 54my 6rve 8jlgm/ap; .35wng, qg.0 MHz (Channel 2) and 80r.e v;w pjg5mn3g6lm/ ,q 8gya6 MHz (Channel 69)?
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in the tuner of an AM ff.0ywsg :a0mq-+bkk 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 96lkccr(8 hu );myk 9hz8.1-$MHz$ 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 capaci+4n bsyvh q.gjlpbz*t.7j+ b5tor $C=840\mathrm{~pF}.$ 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 buil6p- p0udp03ey/y rcp xd a receiver that can tune a range from 14.0 -p06/pdce y0 x3uprp y$MHz$ 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 powb38r6fa r-se/ sxm f7eer 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 electric field of ayl-bd/4of r8s n EM wave. How large r-os4l/bfd y8 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 radi+gu. n6,p+emwmt -r:2ka+rj txri9facally change its output, how long would it take for us on Earth to learn about it?f -gt,.u p9kerr:taj xmi2ma++r6 +nw    min

  Light is emitted from an ordinary lightbulb filament in wave-train bursts abgnpn -u0twt 769b gxlq. .7knhout nk9n7gq6 g 7u 0wnbp-ht ..tlx$10^{-8}\mathrm{~s}$ 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 reach the first astgbf7 8x*akh8nbe:0h 53 dzxaaronauts on *8abxzhe7 0a:5bf a 83nd hgxkthe 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. Belo epc.w-mps.e 0w) was beamed to a listening crowd 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 andep-mw. es.pc0 when the sound left the Moon?    s

  Cosmic microwave background radiation fills all space with an g ra :3g5jf:w+r gyp)ri80iph average energy densi)5fi j+r gri0p8wyg hrpag:: 3ty 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 thy6d2u(*je wgyi4 (x xhat the Earth receix(heu idwj*y62 y4xg(ves 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 trav 5;mw0ztw(yc ueling EM wave is noted to have its maximum magnetic field pointing west and its maximum electric field pointing south. In w tu5w0 (zmyw;chich 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 if it 5f(nuysftc sx5n8/0h 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 an.i4y r5 0ab3z*tqwwq ctenna that consists of a 380-loop circular .wzq b*qtr0a3 5w 4ycicoil 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 signal is 2pg,xzdoxz5;wh v+:m m pt.*j$1.0\times10^{-13}\mathrm{~W/m^2}$ 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 ante5l0 t7 sbm-afs 1rnme.06uvr onna, the amplitude of the electric fa -t0.ms75v6roblr1 u m0efsn ield is $0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitance of a radio tuner consists of six plates connected togna x g7t*9p4gkether placed alternately between six other plates, also connected together (Fig. Below). Each plate is separated from itsxka4*n9gtg p7 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 n q(58fua c7bty gcet/7n6dwrr(p f d6u7)e5lhot 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 ko xgf:0 p7mq4hb7l 2laverage ratefg p4qx k:2l70bhoml7 $P_0$ 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 b;t:bu *yp9 l)/kgquydirections.
(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 statio gmvj,c4x,d w2n.
(a)    $\mu W$
(b)    V/m
(c)    V

  What is the maximum power kv +u p()ei:q*de 0hzvlevel of the radio station of Problem 52 so as to avoid electrical breakdown of air at a distance of 1.0 m from the anu kp)eqzi(v*d0e+v : htenna? 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.]    $\times10^{11}\mathrm{W}$