The electric field in an EM wave traveling north oscillates in an east–0gp5fjcvo yep4cf / 8;west plane. Describe the direction of the magnetic field vector in tp5;p0/v cogycfj8 e 4fhis wave.

Is sound an electromagnetic wave? If not, whara drits-; *x3t kind of wave is it?

Can EM waves travel throu3 p7h 5zce.cpcgh a perfect vacuum? Can sound waves?

When you flip a light switch on, doeh94k-lwwo a4fs the light go on immediately? Explain.

Are the wavelengths of radio and tel5) j li;vv,lolf u*1bzlk8s0j evision signals longer or shorter than those detectable by the human eye?*kjzsiv );vl5,u lf8l1 j l0ob

When you connect two loudspeakers to the output of a stereo amplifier/75oo9y5e mifm k;law, should you be sure the lead-in wires are equal in length so that there will not be a time lag between s;fiw 5l k 5ay9me7o/ompeakers? Explain.

In the electromagnetic spect21fty9;b r,eg,d (j9gisxr ptrum, what type of EM wave would have a wavelength of gr;tpert1(bds9iy xfg9 , ,2j$10^3km$ 1 km? 1 m? 1 cm? 1 mm? $1\mu m$

Can radio waves have the same freq9gwgz4vdrdh +op4k):uencies as sound waves (20 Hz–20,000 Hz)?

Can two radio or TV stations broadcast mm/fo46g;tk ion the same carrier frequency? Explain.

If a radio transmitter has a vertical antu/ cf) dyca3s:sn o pkq8:g5r3enna, should a receiver’s antenna (rod type) be vertical or horizontal to obtain best receptir53qpgn :d:3c/ays fuko 8cs)on?

The carrier frequencies of FM bro tu:apa8ml 7*q:6zssk adcasts 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 signals behind low hills or builusq7lk6p*:8:amz ats dings.

Discuss how cordless telephones b e hwb1tk;uq 5t812vomake use of EM waves. What about cell phones?

A lost person may sisr/;9 r bbo39/: chozs uzltb7gnal by flashing a flashlight on and off using Morse code. This is /bhs/9uc:s ;r z o9borbt 7z3lactually a modulated EM wave. Is it AM or FM? What is the frequency of the carrier, approximately?

  At a given instant, a 1.vjue3+n-oi 3nht*9 bu8-A current flows in the wires connected to a parallel-plate capacitor. What is +j -nuv oi*3nu9b3tehthe rate at which the electric field 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 fiel us/hst;zu0 6wd in a traveling 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 wn +i)fejn*n -f9hsqlo)n1w g8 est, the B field oscillates vertically and has a frequency of wi nh 9lsj1qo))+n efgf8n-*n 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 m57sr5hhp f+woy 1dtu: icrowave whose wavelength is 1.60 $cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelengd6c qn;qt450bodiw0iwbc -d(t te;b* th of a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has frequencyq :y 3,ds nu32pvetxb* $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a wavelem wvul0 w6l22.+irh0f fx6zwength 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 to reach uf* c: :.h.dfb2pwal7ua 4ecqy s from the Sun, $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-wave” radio broadcast band is referred to as the 4ni 0vy:x(cwl4k z)tdngjy9609-m band. What is the dxwiyl0vc 6 9jyg4)(: k0ztnn frequency of a 49-m radio signal?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (other than the Sun) is 4.2 light-years away. Thkx6v clw3 9 5jofugc76at is, it takes 4.2 years for the light it emits to reach vcfjc56u9ko76 l3xg wEarth. How far away is it in meters?    $\times10^{16}\mathrm{m}$

  A light-year is a measure of distance (not ti/vpmodj6b2 y2 me). How many meters does light tra62/2moypdbvj vel in a year?    $ \times10^{15}\mathrm{m}$

  How long would it take a message sent as radio waves frodoxz nwty/m5j7+n +ji*;g *ohm 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 experiment to a sizvsd*-3rn x5s+yq0uhg 7s m:ai zi37ofe that will fit in one room. A six-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 * s7mssygz 3viuo30rf:d nihx a7-+5 qmust the mirror rotate?    $\times10^6\text{ revolutions/s}$

  Who will hear the voice of a singer first — a person in .q)dluv2j /tg*o ive 5the balcony 50.0 m away from the stage (Fig. Belo*e.gouq5/id)2l v v jtw), 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 /2klw lm3xv1ns sv 5a3of electromagnetic e ss31/m v2vkwlan3lx5nergy. 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 an rms strength uo )cej)1fhrxrvg :39of 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 t/gi 6 w65jzzo8) dswczransported 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 a distancifw56 : :t+wp ;3ivdnug6tqxme of 10.0 m, what is theidn ::gi wwx;tufp53q 6tvm+6 average intensity, 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 average power outputtd 9rpw hk b3o;mrs4./ 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 0in ;zhzpomfe,*u1 q 5an 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 emp-m ri 7oa1.gmbjc) wyse25k-its a 1.0-ns-long 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 press,i m0oz,px4oddh, ;qbure due 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 wav: ny vv5-wueglga b400elengths 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 recojboa 2vjf 75+,n)uu peption.    m

  Compare 940 on the AM dial to 94 on thsha o qczs:j0t0)7.ph.y 6jtt e FM dial. Which has the longer wavelength, and by what factor is it larger?q).t sj.j7yh0p z aht0cost 6:
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths for tw*u ca8/bpn qeu;n n34do TV channels that broadcast at 54.0 MHz (Channel 2) and 806 MH;*bdn u uqe a8/4pcn3nz (Channel 69)?
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in n +xfetljtov0;w72 eck/h ;2 nthe tuner 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 96.1a*+w4*5r3tswkd q wig v 6nc2a-$MHz$ 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 fixedz5x,q -)nsk go 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 tunn: 9el+jwmx p)d;sw y-e a range from 14.0lj d9wp:msxy+- w;en ) $MHz$ 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 radiatg;nf dpfds6+ d65rn4qysu40g ion 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 parallel to the electric field of g)wrxm:9tkv.mv55.zyg h jo( an EM wave. How large must the electo .g)(5j5kyt.:wx hrgmv vz9m ric 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 radicallyojlvn9 p);y a5 change its output, how long would it take)vpna 9;l jyo5 for us on Earth to learn about it?    min

  Light is emitted from an ordinary lightbulb filaff-vr0m0p+x yrwrpd qn /*+j3ment in wave-train bursts about f+q3x/frjn vy rp- r+ pdm00w*$10^{-8}\mathrm{~s}$ in duration. What is the length in space of such wave trains?    m

  (a) How long did it takt15v 86ttemxs5k v)mg .dbd *ae for a message sent from Earth to reach the first astron*mst8 vdg5m.d5b) 1tvt eka x6auts 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 th,3 budxs/q3vpe Moon (Fig. Below) was beamed to a li,3/bs p uvdx3qstening 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 radia,yfrck x2 (;sd982h 5 oxiyetvtion fills all space with an average energy densitr5y2 c(hixe28;dkyox9tf , sv y 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 thuo*y4hldcxr:ro 6r74nj t )q8e sunlight that hits Mars, knowing that theoo h4j )nur8t4yr*cdxq7: r6l Earth 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 time, a traveling EM wave is noted to have its maximum/0zg xq2ku gv o7giv*eis7o -3 magnetic field pointing west and its maximum electric field pointing south. In which direction is the wave trav 7vgv/i0* 3x7ggoisku2ze q-oeling? 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 wegr3m5z3oz h6b0vsa8umq *) wqre
(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) .e el3bjl8(zkz mv5 mofa3zv:b(e/:z will be generated in an antenna that consists of a 380-loop circular coil of wire 2.2 3zbzl : f3a:o/ 5ekvb8l(jzzm. (veme $cm$ 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 a5 3vcgsw ;8ndstation’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 ampliaq4 8h:/: v*8ykatel7np3n rpdimha2tude of the electric field is 27 vm:ppth8l3qa*dkn4y ra:/a 8 enih $0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitance of a radio tuner consists of six ploo qw27rbka8rc7 b9*lates connected together placed alternately between six other plates, also connected together (Fig. Below). Each plate is separated *k27qw 7rbb9ocar8 ol 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 all63di slrwf.hn tob/*2owed to broadcast 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 u7ua,e ,g tzl6;ae1 wppniformly in all directions at an average rate pu 17eatl6a , p,ez;wg$P_0$ 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 un;x xzc 2q;pnlx lr96b5iformly 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 statiotg)e pxt6.s;t ycj/62rccl7 kn.
(a)    $\mu W$
(b)    V/m
(c)    V

  What is the maximum power level of the radio stao1gztzn6wwy:uk4lu.3 p f0 k1tion of Problem 52 so as to avoid electrical breakdown of air at a distance of 1.0 m from kfpw.1 u3z y6owkzg1t4un0l :the antenna? 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.]    $\times10^{11}\mathrm{W}$