The electric field in an EM wave traveling north os5j uyo 23.nz3qz*-g8fj9 nvmkg xdyj6 cillates in an east–west plane. Describe the dirn6ujz vz-.gdnj5kx9g oyq83 fjm3 2*yection of the magnetic field vector in this wave.

Is sound an electromagnetic waveag(yf4.u: h hrs/k7mk? If not, what kind of wave is it?

Can EM waves travel through a perfect vacuum? Can egk7 .2, gtst ulb6w7usound waves?

When you flip a light swi)on v s my9)z9mha3u ew0co):ci)t6z ntch on, does the light go on immediately? Explain.

Are the wavelengths of radio and television signals longer or shorter tf)nqwt w4zp + sa(t6;f/ sb3dfhan those detectable by thesdwf ; (f3q wnpab +tt/)4f6zs human eye?

When you connect two loudspeakers to the *)1fjc bg, .vbj jn)thh-kb y0output of a stereo amplifier, should you be sure the lead-in wires are equal in length so that there will not be a time lag betw)*-v h)nbbyh,b1k.c fj jtg0jeen speakers? Explain.

In the electromagnetic spectrum, what type of EM wave would have a wh2j,oji qh6k; avelength of qh2 ;j6 oj,kih$10^3km$ 1 km? 1 m? 1 cm? 1 mm? $1\mu m$

Can radio waves have the sa5mc zb2rll8oui6 *2;fafqdg3me frequencies as sound waves (20 Hz–20,000 Hz)?

Can two radio or TV stations broadcast on the same carrier fre0fnl 1wcfj5-q a+/ uubwhm.;j02ghr equency? Explain.

If a radio transmitter has a verti9e ; d7oie.rvk*o9o8xa ywrj7cal antenna, should a receiver’s antenna (rod type) be vertical or horizontal to obtain bxyer*oao ;ow 7v j.e9 k8i97drest reception?

The carrier frequencies of FM broadcasts are much higher than for h.orz;-5zlju 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 h-hzoz j;5rul .ills or buildings.

Discuss how cordless telephones make use of EM waves. What about ce3o-n y(/1:txkc bjoeu ll phones?

A lost person may signal by flashing a flashlight on and off using Morse cod0 0nhtmryyvsv 3u)/5x e. This is actually a modulated EM wave. Is it AM or FM? What is the frequency of the carrier, approximately?05y0r)3ty mhsx/v vnu

  At a given instant, a 1.8-A cu5 * kcbktstxi5q h,w;/rrent flows in the wires connected to a parallel-plate capacitor. What is the rate at which the electric wt /;5 kix,q*hbkt sc5field 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 v18kd1/ djb;kcew t4i 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 travelmd,82jr 0jl miing west, the B field oscillates vertically and has a frequency olm2dmijr0j , 8f 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 whose wavelen wqab- j r:i(kjw0qx+*+/yqjmgth is 1.60 $cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelength ofbg.2 a avkj*du.(k5z m a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has frequen1+ fctdwc -s(,5 6qvfg pz lc:yyxng79cy $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a wavelength of 65t) n; kw 7vjtyo;kz;o(0 $nm$. 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 Sun,9j1 f,96m xu (jpkylqr $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-wapyk:wi8wp oh*wh a556ve” radio broadcast band is referred to as the 49-m band. What is the frequency of a 49-m radio signw85hpahpoik *w5y w6:al?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (other than the Sun) is 4.2 light-years away. That is, it takh 1ypilp)lx)(tu4smxl w5 /+4v5f vmoes 4.2 years for the light it emits to reach Earth.xv)x/t fl h4+op(psv 4i) ll5mwu my15 How far away is it in meters?    $\times10^{16}\mathrm{m}$

  A light-year is a measure of distance (not tic+ wiqruen xyh 4/.oj1y- w.p0me). How many meters does light travel in a yearn ./- 4+jyx1 0qrhyowcieuwp .?    $ \times10^{15}\mathrm{m}$

  How long would it take a message sent as radio waves from Earth to reach Mars ht5qr6+ rr9 pn
(a) when nearest Earth,    s
(b) when farthest from Earth?    s

  A student wants to scale down Michels iwf,tow+z 0((vcj 1;3xhzcjcon’s light-speed experiment to a size that will fit in one room. A six-sidezwzwx 1,cj+3((vit ;f ccjh o0d 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 voice of a singer first — az*)q z -chc,mdn1c8xm; 8b ggb3 j1)f ydzqsk* person in the balcony 50.0 m away from the stage x-k1mbydfc jcd3 qg mq1bz)8*zz); c,*shng8 (Fig. Below), 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 electroc7 y9i)vj u1edhx5xp; magnetic energy. If the laser light waveu)jxch v5e;x1 9ipy 7dlength 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 of 28.x ed-t- 50lb 4h*dr(wm5wvy zr5$nT$. 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 across asw2, ,4ikg yfc $1.00-cm^2$ 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 distanceatgifw6-+e o7 of 10.0 m, what is the average intensity, and wt wf-gea6 +oi7hat is the rms 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 posn1oe;e-k-6 e fow)q ds/zt.rwer 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 t47/wih1 *irrh npb ,cjhe 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 average powerjjhrj2 ut6l s5r qvh/9*eu-r0 $2.8\times10^{11}\mathrm{~W}.$ 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 zf27dz8x)bc u 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 wavelp ctr+jf-6w+ tr q)x)j2yqur;engths 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 reception. wjf4(otk9:hj   m

  Compare 940 on the AM dial to 94 on the FM dial. Which has the longer w)d0f avpgics-,77lwn - dg7p javelength, and by what factsj7vwg0 pd-anl)dfic ,p- 7g7 or is it larger?
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths for two TV channels that 8s5df+p7mulonn7l uv2akzb+/vq0sa/ ,ss y2 broadcast at 54.0 MHz (Channel 2 bdssq0 smnvzna//2vlfup2lko,7 5 a+s+ u78y) and 806 MHz (Channel 69)?
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in the tuner of an AM ra pcw/ p,gk4 f: gwk/hy9b )gt4gsma)0bdio 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.b 4lm3vey ,gi51-$MHz$ 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 hexp;pa ; *sap*w:a/amas 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 operator wishes ta3hz 4i,jz59vuat7uz:no-5 xlxy v.ho build a receiver that can tune a range from 14.0 aoz - 7x:yvja u9z4zni53t5x.hhuv, l $MHz$ 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 poxzp-xiadxc5 * l. d5h+wer 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 ante4 z2ru:ya7mf wnna is oriented parallel to the electric field of an EM wave. How large must the ele:2zma u4f y7rwctric 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 0rq:b18t px,qyg *wpgor somehow radically change its output, how long would it take for us on Earth to learn about ipg,qypt1xw8 *: g0rbq t?    min

  Light is emitted from an ordinary lightcjtc5b r/8z4nk1 h eiz/o tn)*bulb filament in wave-train bursts about n c ekziz5/ n 81to)jcr*4hbt/$10^{-8}\mathrm{~s}$ 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 aslk +sqct+l+jz08or( ltronautrl+ ll+ +oqjc0z(ts 8ks on 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) wa8 -4c()ize2lk m qzwfls beamed to a listening crowd from a radio speaker. If you were standing 25 m from the loudspeaker, wf qz 2m-el8 4i)cwl(zkhat 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 an average energyn):qwfse*9d o densitd fw:*q ne9)soy 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 f:imo c gz2n; vtga:(7eield in the sunlight that hits Mars, knowing that the Earth receives abouv(:gge; a: mno27tczi t $1350\mathrm{~W/m^2}$ 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 g ,z3gc z9 *d41/bwv0brfeowonoted to have its maximum magnetic field pointing west and its maximum electric field pointing soutc/z4wor zebg0ob9*w v d 1gf,3h. 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 be if it werepp;w91,slr ;joqphs9
(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 consists of a:fn q8le:qppdh7 x2m u1.ztp/ 380-loop circul/dph :xqfe8mq2lnp7 pt1z. u: ar 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 signa 6td;m yig-wvta61 r4:sniha7l 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 amplitude of the elec7 p,tf+c0 0wvdeyodlu1 9-zq57xus ug tric fu59d7 ,1+0e -lzwtf 7x0 dguoqspcv uyield is $0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitancjkaa90ag9d9j i: sx 2le of a radio tuner consists of six plates connected together placed alternatga9 s x:di2jkaajl990ely between six other 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 2 3fih3sg6gf 9w5 $kW$. 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 direc ti+o/q9/px:twocgv /p ja16r tions at an average ratetc/qa/i+jgp9rwo/ 61 vxo:pt $P_0$ 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 unifxlz reu3 7-/asormly 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 100cux2 b -mzltu5+h l d4p/0b(stq0bhs8 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 so as to nvm*,lybx5:qxk dzm4 10/ku cavoid electrical breakdown of air at a distance of 1.0 m from the antenna? Assume the antenna is a pkc4 qdvb1xkuz 5,nxm/: my *0loint source. Air breaks down in an electric field of about $3\times10^6\mathrm{~V/m}.$ [Hint: See Problem 51.]    $\times10^{11}\mathrm{W}$