The electric field in an EM wave traveling north oscillates ip ,4db 51l)p(jb pe7kxtdsk+ tn an east–west plane. Describe the direction of the magnetic field vector in this epkdpsd) ,p(+lx4 1b tjtk5b7wave.

Is sound an electromagnetic wave? If not, what kind of wbc5z* v: hxv8mave is it?

Can EM waves travel through a perfect vacuum? Can sound waei gl3p-a3 h5bves?

When you flip a lightfs4u vz+d*ozw7o8zt1/d w.n f switch on, does the light go on immediately? Explain.

Are the wavelengths of radio and television signals longer or dmm;b q -rm6u: zqy+ky3:do d )9/zcbbshorter than those detectable by the oby /6by:z93 b)qrummd +-k;d mdc:qz human eye?

When you connect two loudspeakers to the output of a stereo amplifier, should yq16zwl r:c6/ ps4mxtdou be sure the lead-in wires are equal in length so that there will not be a timeqszd :/wxct6 r6m41 pl lag between speakers? Explain.

In the electromagnetic spectrum, what type of Edvj u9cnipm6e2zr8:*3h ha -cM wave would have a wavelength of nc2mv368-uh* phcjir:e a 9dz$10^3km$ 1 km? 1 m? 1 cm? 1 mm? $1\mu m$

Can radio waves have the same frequencie6xk3x e. bk 08*0y4ojwmqifuds as sound waves (20 Hz–20,000 Hz)?

Can two radio or TV stations broadcast on the s(f y5wmlzny+ 4 d-axbg*e7pu5ame carrier frequency? Explain.

If a radio transmitter has a vertical antenna,tt )mv8a:4z.g j0 dnkl should a receiver’s antenna (rod type) be vertical or horizontal to objga0t).v tn4l8kmd: z tain best reception?

The carrier frequencies of FM ; : wu+jxzx8)qea4znubroadcasts 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 moreux)+euz 4w;xnj 8aq:z readily than FM signals behind low hills or buildings.

Discuss how cordless telephones make use of EM waves. Wozb/+ y/rg+ x9(dub b u0n)tfmhat about cell phones?

A lost person may signal by flashing a flashlight on and off using jbsr q9ig175, i (kzvoMorse code. This is actually a modulated EM wak7vr g1sji( q 5izob,9ve. Is it AM or FM? What is the frequency of the carrier, approximately?

  At a given instant, a 1.8-A current flows in the wires connected to dbo .9wer(z;yca31jdp ny9x6a parallel-plate capacitor. What is the rate at which the electric field is changing between the plates if the square plates are 1.6d1wpo e d;b9xy (9nc.zyar6j30 $cm$ 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 aw+zsmaocvdb ql+ c (;c3h3+i ( 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 verticalld)xd(q9sazol *9kwuq+oxpm .m e x:0 .p 7li.uy and has a frequen.u d xmx7( .x.q9i:+loqmwk o a us0ze)d9pp*lcy 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 frequenca:e.3zmue c.cuhi8t7y ; d9 bey of a microwave whose wavelength is 1.60 $cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelength o2aa-rwv(d:r0tbo ,sz f a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has frequenf, fh+z2 gwt0 b,7yw ez7qfbus:u 1r-acy $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a wavelength of 651 oit (m97hhdl0hquh 30 $nm$. What is its frequency, and how would we classify it?    $ \times10^{14}\mathrm{Hz}$  ----待选择----visibleinvisible 

  How long does it take lig2 i y4 *lz*a2oiy)wnlg dq0t.nht to reach us from the Sun, $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-wave” radio broadcast band 8 xmo08 3 wpb3i1xsygiq t8q-mi*5hhwis referred to as the 49-m band. What is the frequency of a 49-m radio sign iigqx 8-*wt8qb0sw 1mh35iym8 o hpx3al?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (other than the Sun) is 4.2 light-years awao; 949lhlu:xhnup )vny. That is, it takes 4.2 years nxvpo9unl 4 9lu h;h):for the light it emits to reach Earth. How far away is it in meters?    $\times10^{16}\mathrm{m}$

  A light-year is a measure q5rsbn pt// 1ynsbe)( of distance (not time). How many meters does light travel in a yeaer/sbsn (ty1nq b5)p/r?    $ \times10^{15}\mathrm{m}$

  How long would it take a message se0ks*;eu4/r qa-8i ,beo19wv d rxpsc rnt 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 Michelson’s lighse2 o21of+x sxl7bl-vt-speed experiment to a size that will fit in one room. A six-sided mirror is available, and the stationary mirror can -b x2v o1es2solx f7l+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 voic ,q 5 10dia3np*yreszxe of a singer first — a person in the balcony 50.0 m away from the stage (Fig. Beln*dp5sq,a01e3 z xiy row), 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 electrob6 mt5.;hsrne magnetic etsm.5hb 6; ernnergy. 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 a3rw ,qp -1dab(gjnba-ec 4q e;n 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 transported3)x;r vaghj m + mp8 h5n8:b-pv8bvyrv 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 sddlsxdi4d/ 2m r88w 4gource. At a distance of 10.0 m, what is the average intensity, and what is the rms 8dsil r/8w 2m d4dx4gdvalue 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 power ougx 65wh.onu 1;5o.as0 2k9l8x iyzxf.msxcsrtput 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.4/h 6qd zhtxs 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 ofi lws ggny 82gc/o/, jt50c5ik 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 bulb at a di h0-cglnw1ju67 grhkyf5- ,lzstance 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 kp w5zy nw+7g/
(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 phohu,,vq -vn: q;+es g;ln g;iwsm;9qwene reception.    m

  Compare 940 on the AM dial to 94 on the FM dial. Which has the lgzkwr 7/py6szfm *80konger wavelength, and by what factor is i0z8gkprsf* 7 z/mky6 wt larger?
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths for two TV channels that broadcast at 54.0 MHz (Chanco/ o+:n zqp 8b).jrnanel 2) and 806 MHz (Chan /onq8zno ba jc+.r:)pnel 69)?
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in the tuner of an AM radio has a capks k-5.g, ( larusw3iyacitance 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 h0mi hns f28hh )cp2vq*k/ xw/96.1-$MHz$ FM station has an inductance of $1.8\mathrm{~}\mu\mathrm{H}.$ What value must the capacitance be?    $pF$

  A certain FM radio tuning l)lm r:6 t uryuc,u)5tcircuit 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 operator wishes to build a rei 82liufw, f)yjzi8i4ceiver that can tune a range from 14.0 4 zyff8 u2li,)ij8i wi$MHz$ 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 power of 1m-inm) j1 tq:v0 $kW$ 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 l wm,bvetbbv/b.98m . field of an EM wav/8mtbb.vl ,ew vbb.m9e. 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 radically change fkq gqq7qya,-x*( o7/:i snei its output, how long would it take for u7ifn q yaqk,e:-oq* x s7i(g/qs on Earth to learn about it?    min

  Light is emitted from an ordinary lightbulb filament in wave-zztbio56n* 4 rtrain bursts about bt5i rzz46on* $10^{-8}\mathrm{~s}$ 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 (d-gt ua r8mz)-q,1)vvltmng first astronauts z(lnvgm1)8r ,tv u) d -qga-mton 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 oqu5od vg,e 63dn the Moon (Fig. Below) was beamed to a li3q uv6de,g5odstening 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 and when the sound left the Moon?    s

  Cosmic microwave background radiation fills alekj id,.bf9 s*ob 2y8ol space with an average energy densi 9*seojkof8.i 2,dybb ty 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 thez;jqr6l2t +aq ys r3/t Earth receives ab+ r r6l3ts2q/;yjaq ztout $1350\mathrm{~W/m^2}$ 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, af g 0ksq bgdbw)w5)p1) traveling EM wave is noted to have its maximum magnetic field pointing west and its maximum electric field pointing south. In which direction is the wave)1w q))bsk5dw0bf gpg 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 an8rp xzi7;ei xca3g9j6(u9j tjtenna would have to be 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 be generated in an antenna that consists of9,jf4(x31lqvg0 ;k nft a 5 pmc+ewbda a 380-loop f gvflkp5xd,+9a(qt c;w0j 3ba4mn e1circular 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 TVn/o b;,r3c-fr pxuz o1 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 of *u 22af/m z8k .e0chp3fyoohkthe electric fielko.f/2p*uchzefyo 80h 2a m3kd is $0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitance he2zx e- e5-l:g mq.nfof a radio tuner consists of six plates connected together placed alternately between six other plates, also connected togf2 :xge -m.-hnqlez5eether (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-a+ ncq.u3 4;skemdsymw)6+1jsdx l x 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 directions at an average rvt+xi-9c e48e3 cu ubcate 8ucve i xb 394-utcce+$P_0$ 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 vo atje,57ayl+b c2e5 3aiuf: 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 diu r,* fs05(kgdjwa2r d d5zu+sstance of 100 km from the station.
(a)    $\mu W$
(b)    V/m
(c)    V

  What is the maximum power level bo nsqgk3w2- 6of the radio station of Problem 52 so as to avoid electrical breakdown of air at a distance of 1.0 m from the antenna? Assume the k2nwb 6so-g3qantenna is a point source. Air breaks down in an electric field of about $3\times10^6\mathrm{~V/m}.$ [Hint: See Problem 51.]    $\times10^{11}\mathrm{W}$