The electric field in an EM wave traveling north oscillates in ax l6uv +1t7pie3flo)c;tod a3n east–west plane. Describeilxav pu; 1ttcdl7)6f3+eoo3 the direction of the magnetic field vector in this wave.

Is sound an electromagnetic wave? If1eie zpb *bk0t;,b2fk not, what kind of wave is it?

Can EM waves travel through a ,ex seh//) 6bc0os wyzperfect vacuum? Can sound waves?

When you flip a light switch on, does the light go r60 ik5h93prwjsy ;jxon immediately? Explain.

Are the wavelengths of radio and teleix asxl09o( z9vision signals longer or shorter than those detectable by the human ax0o9zi ls x9(eye?

When you connect two loudspeakers to the output of a steu ke,y ;yk.t6zreo amplifier, should you be sure the lead-in wires are equal in length so that there will not be k; ,yze6u yt.ka time lag between speakers? Explain.

In the electromagnetic spectrum, what type of EM wave w/7i +ama5nak7b 7vf vbould have a wavelength ofbn +bi7aaa 57/ fkvv7m $10^3km$ 1 km? 1 m? 1 cm? 1 mm? $1\mu m$

Can radio waves have the sam,. cb5qblr.n9jm 6 lxje frequencies as sound waves (20 Hz–20,000 Hz)?

Can two radio or TV stations broadcast on the same carrier frequency? E653m0q ggkgh6ygq8 zz-up - btxplain.

If a radio transmitter has a vertical antenna, should ad z9:mma+ 8 y1*sljbpq receiver’s antenna (rod type) be ver8+a:bq smyj*d m1l9 zptical or horizontal to obtain best reception?

The carrier frequencies of FM broadcasts are much higher than foryx.y-nt6 avmv rr:q;7 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 hills or buildinytqnv :-xv 7;.yar6mrgs.

Discuss how cordless telephones make use of EM wavesaehwky 42e(oi55fq 60jc md8z. What about cell phones?

A lost person may signal by fukif ly( 9h5+ulashing a flashlight on and off using Morse code. This is actually a modulated EM wave. Is it AM or FM? What is the frequency of the carrierlihy9+u ukf5( , approximately?

  At a given instant, a 1.8-A current floms21yml 3qn -1ox u tq*6kej4ows in the wires connected to a parallel-plate capacitor. What is the rate at which the electric field is changing between the plates if the sqmoqe3m u*n 6 xj yl1qt-s4k12ouare 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 EM wave has a peak magnitude ozlr oen*: x6 az/vm89ef 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 osxo;-bv crpd *7cillates vertically and has a frequency 7v-probd *;x cof 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,osr3k4wt m9 dce r* qh6f,)qogth is 1.60 $cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelengoyh9v y; o:yh0th of a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has frequen kfj+5s- rsls)cy $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a wavelength oa k.7ve;pg.wm f 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 us fro2;n r rgeb:iuy/0dz8ds95ofd m the Sun, $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-wave” radio broadcast band is refer*mx4(jtwe -nnic h,wc ;94mpered to as the 49-m band. What is the frequency of a 49mmhx4c4i;nwn -e*w9 cj(e,t p-m radio signal?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (other than the Sun) is 4.2 light-years away. ykg13fbv l:4 8t4uysaThat is, it takes 4.2 years for the light it emits to reach Earth. How far away is it in met :fbly4vgs1 3u4kat8yers?    $\times10^{16}\mathrm{m}$

  A light-year is a measure of distance (4emu .axvcxr4( d w);anot time). How many meters does light travel in a vxc w .;dux)e4(am ar4year?    $ \times10^{15}\mathrm{m}$

  How long would it take a messagexr9wb qc*h/ j8 sent as radio waves from Earth to reach Mars
(a) when nearest Earth,    s
(b) when farthest from Earth?    s

  A student wants to scale down Mic6; ame95dlct p2 p/l0ahsyk,qhelson’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 fro6a ,a5yd lc /q9m;tplsphe k20m 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 — a pz fn 8vxrmo3a ( d0gbtte(l569erson in the balcony 50.0 m away fr dgl85b(93e6(ttfznx 0va orm om the stage (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 shodtm c7zbi6:ar2(j-n mrt bursts of electromagnetic energy. If the laser light wavelengtn-(:atim j 6dc2mb z7rh 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 4a qc:mzy0fm -hgl.0d a traveling 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 tr;*x-g d19; j;*btb+fj(mzxrwf ibuc eansported 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. At oy3x70-l,6 cy)39fj uwnm lwjpwag(o a distance of 10.0 m, what is the average intensity, j -olfyp)am(n6 9 uxl3w7yjw03,ogwc and what 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 averagey b n5do/db)z)mtnek v: zd q3:6fv;j4 power 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 o6 b8xn.vk1 zc2ada.pfield 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-lon84,v,a zb:kf/so v ew)sbjtj,g 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 100-w 5is5q6tq5nu 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 waveleng-h h n4f(rpu.jolp22lths 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 , ck. klrh7em;hj-mu5phone reception.    m

  Compare 940 on the AM dial to 94 on the FM diarsjvo3g *w*j*fp iaswit;;35 l. Which has the longer wavelength, and by what factoi*ar sg*3 jp3f;v 5wi*wjtos;r is it larger?
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths for two TV channels that broad+sgf,6l. l wrocast at 54.0 MHz (Channel 2) and 806 + ,6osr.llgf wMHz (Channel 69)?
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in the tuner of an AM radio has a capacitance y.8 /lsb0fbjm 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 9dc ,s dw-vky 8zo3cu:d-o)o7b6.1-$MHz$ 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 fixed7apa44oyg) 5 g5khnc/tgdg 6*p kwjp1 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 tune a ranv3yde.ujd1n;p4n ;e rx cx( 4pge from 1cyj;3n44 ;1xpdvdeu(p re.xn 4.0 $MHz$ 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 ahi 4m6v-0 seqnx ,5xvp 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 parallel to the electe2rwf88 q3 lsim ::zokric field of an EM wave. How large must the elk solq:rifwmez28 : 83ectric 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 output, hoi rkcuu r0* t1//xl5dzw long would it take for us on Earth to learn abor u t*0luk zi/drcx5/1ut it?    min

  Light is emitted from an ordinary lightbulb filament i7 (ptnng :/y8xvx.3hh1 rsigyn wave-train bursts about r h:8 sg g/.pihnxxyyt(7n3 1v$10^{-8}\mathrm{~s}$ in duration. What is the length in space of such wave trains?    m

  (a) How long did it take for a 3,a93gjp ((kw8qcergze k3yh message sent from Earth to reach the first astronauts on the hgez(e j3r89kk (yw3gc,q pa3Moon?    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 4c ui op/6 ad t2nqv3sxyx:3-afrom the Apollo crew on the Moon (Fig. Below) was beamed to a listening crowd from a radio speaker. If you were s2a:at6 s xyqvuo-xip4ndc33 /tanding 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 background 1 0qlu dj-; i3d2/qd3pn uspehradiation fills all space with an average energy densitye1dp h/2uls qq 0jiu-pd;nd33 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 g+m8kke f+:91/zrj i okif )osMars, knowing that the Earth/ z9rkik ioeo:+k+g)1mf j8fs 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 ti1fw v 7j 2nd wqotuayeb0g4, wq.sz0c3x43k h;me, a traveling EM wave is noted to have its maximum magnetic field pointing west fbheyq3.k7; d,sjwu2 qw xowv44 tg31n z0c0aand 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 be f wsbg/y1; rw7if 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 an6ze+hi ly/qy-xl:k x,m:w s0q antenna that consists of a 380-loop :q6s lx0yqhlym,/i :-+kewx z 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 8. iej 1zpya;scf, vyryqq -/6a 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 amplitude o3bmhb:uvr0o/ f the electric field i u:bmo/vb3r h0s $0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitance of a radio tuner consists of six plates conne3z *til*8t ;lz i,etx8kwo 0nlcted together placed alternately between six other plates, also ktl *z i;0*i8l8z 3l, nxwteotconnected 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 exqi u) 96;8r yoszvbwj-ceed 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 iy4h 7w *3midz qbjhx,/okf /s+n all directions at an average rate+ f* 7qmwjis bdhk/4x3z/ ,yho $P_0$ 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 directions. 3qztyxzo2*+p
(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 distorg50pgyn.g -na 4b*,d sf gy(ance of 100 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 rh *5ndf(q oe(to avoid electrical breakdown of air at a distance of 1.0 m from the antenna? Assume the antenna is a point source. Air brfd(o*( enq 5hreaks down in an electric field of about $3\times10^6\mathrm{~V/m}.$ [Hint: See Problem 51.]    $\times10^{11}\mathrm{W}$