The electric field in an EM wave travewdpf:lav d+a-;xztjh4c .v, .ling north oscillates in an east–west plane. Describe the direction of the mag4al,c+daxptd vhw. jz.:;- f vnetic field vector in this wave.

Is sound an electromagnetic wave? ,cvszc7z ; t7rIf not, what kind of wave is it?

Can EM waves travel through a perfect vacuum? Can sound waves - f qmi6po;97xp)vpkijib6 9y?

When you flip a light switch on, doev*)5dt ul bgtpvvgq 74n/j g:,s the light go on immediately? Explain.

Are the wavelengths of radio and television signals longer or shorteh 87w 7muvfbh1r than those detectable by the humanf7 vwh7u mh81b eye?

When you connect two loudspeakers to the output o 2wyrqn 1hpi5y,zv08jf a stereo amplifier, should you be sure the lead-in wires are equal in length so thryvi8y,0p 1z 5qwj2 nhat there will not be a time lag between speakers? Explain.

In the electromagnetic spectrum, what type of EM wave would have am,b/8 netop (z3klk w6 wavelength ofntb 8/pml3 ,kkwez(6o $10^3km$ 1 km? 1 m? 1 cm? 1 mm? $1\mu m$

Can radio waves have the same frequencies as sound waves (20 Hz–20,00,ptrf hl)l6vd94e ea5w/a hm.8 0ywvyje g:j;0 Hz)?

Can two radio or TV stations broadcast on the same carrier freque*x6sruzl ( uq4ncy? Explain.

If a radio transmitter has a vertifoja1d feiu9 (89m9 fical antenna, should a receiver’s antenna (rod typo 99(u1f89jfi mfd aiee) be vertical or horizontal to obtain best reception?

The carrier frequencies of FM broadcasts are much higher than for AM broadcast9o8a13iu;du t -8iyiwaab9sug5zyg* s. On the basis of what you learned about iaauwi8 5b9z3 ;aiy -guoty81*sud 9gdiffraction in Chapter 11, explain why AM signals can be detected more readily than FM signals behind low hills or buildings.

Discuss how cordless telephones make use of EM waves. What abourx6m8za3s x y9t cell phones?

A lost person may signal by flashing a flashlight on and off using Morsee) r f1e5xcs*k code. This is actually a modulated EM wave. Is it AM or FM? What is the frequency of the carrier, approximatck rsx)5ef*1eely?

  At a given instant, a 1.8-A current flows in uedt-4c6nolc2j (+, 0cah74mq iwx vbthe wires connected to a parallel-plate capacitor. What is the rate at which the electric field is changingex7cb +c vw0hmo4n,6it- dlaj 4q2uc( 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 travelingg qwcsjc6lc -9fi(4s9 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 field oscillates verti07bqa7u kryd..n9yarih4wlpr (1rb+ cally and has a frequency ofhkda..brb rrnyly 77u1arpi9q(4+0 w 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 wavelength is 1.60 / gfb1 pqn1mkc* b1pu($cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelengtad2 dahna71c29 a b;- yehpni/h of a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has frequ pso4qydz0/b 1etmzu-.z 98pcn6y x3x ency $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a wavevqf,t//) +e z vtwl5hflength 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 to1hmvfs/u- q-b .(buq t reach us from the Sun, $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-wave” radi:sm xnyg3 ojigld5 ;rd n2j.7t9n9b5xo broadcast band is referred to as the 49-m band. Whalx;y7bs52g9n :jnng 9jd35 ti ormdx .t is the frequency of a 49-m radio signal?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (othe. :sswd; ge0xbr than the Sun) is 4.2 light-years away. That is, it takes 4.2 years for the light it emits to reach Earth. How far away is it in meters ss 0;g:wbxd.e?    $\times10^{16}\mathrm{m}$

  A light-year is a measure of distance (not time). How many meters doetjc lc77(mcp b6 kgo26s light travel in a year? 6tolb (2jkgcmc c 6p77   $ \times10^{15}\mathrm{m}$

  How long would it take a message sent as radio waves from Earth to reach hyv6dwd5;,++v vx an zMars
(a) when nearest Earth,    s
(b) when farthest from Earth?    s

  A student wants to scale down Mar sf q8/;5gjqichelson’s light-speed experiment to a size that will fit in one room. A six-sided mirror is availa j a58g/qf;srqble, 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 9ci d sh-80i9l4ddbxf of a singer first — a person in the balcony 50.0 m away from the sta0ifscx8 d4 b l9d9-hdige (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 sciencx3ffqx f6nr1ee01min 5z e3d.e and medicine produce very short bursts of electromagnetic energy. If the laser q1inz mf 0 16.35fn3dx refxeelight 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 v7qhqhv+71zdq qx- 3ian 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 tts th6d2 n,t.hransported 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-Whhfhe1/ )6aq sh2tm )m source. At a distance of 10.0 m, w q)h h2mhfa6e1stm/h )hat is the 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 pow(t4x)wxztf b p82ao /ner 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 field0hng7p85k t 4 rirk5co 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 pulsl2s6.:cnw 8/fczd nsy3e jiz3e 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 bulb at a dista5 oboyo4ja-dpqd 2o 5.nce 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 wavelengt,bux .,as/qwp hs 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 for41tnv,lc3 **tp. /i fclayye2zmxk x* 1.9-GHz cell phone reception.    m

  Compare 940 on the AM dial to 94 on the FM dial. Whe4,q3dah 6yl rich has the longer wavelength, and y aq6ehl3d, r4by what factor is it larger?
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths form r90q6b4wg ph two TV channels that broadcast at 54.0 MHz (Channel6gr0qbhp49w m 2) and 806 MHz (Channel 69)?
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in the tuner of an AM radio has a capacitance of 2800 n6j;:adyuqj.-y oh+ v$pF$ 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.j0 *aq9tf faw/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 circui(4/z5wq(ra k izk:5fmir wirczn o /m;l; w5e*t 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 re6 ml/hmdi9t)vceiver that can tune a range from 14dmi hl69t) mv/.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 a p4 jgpy13gdn 0iower 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 electh/iaqi yfz;wi- v4urd q(06 71zcy; rhric field of an EM wave. How large mr( y;h0/vzz4;i 6ciiqf1-uq7ry a hdwust 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 m); hxl4e*ptugvh +6 fchange its output, how long would it take for us on Earth toh hxulp)f6*gv;+em4t learn about it?    min

  Light is emitted from an or kkkg; / qn,r2wb/fcr2dinary lightbulb filament in wave-train bursts about ,/kgkfqb/r 2cn 2rk; w$10^{-8}\mathrm{~s}$ 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 i7 iu5edvbj)2vt 5p1f+md*0grzy(b athe first astronauts on thiz(0*bdf+t5 b1 ra m gvu )ji7depv2y5e 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 Apolldbs, 78w (fy ipbmq*+do crew on the Moon (Fig. Below) was beamed to a listening crowd from a radio speaker. If you were standing 25 m from the loudspeaker, what was 8pb +d s,7qywd *mbi(fthe total time lag between when you heard the sound and when the sound left the Moon?    s

  Cosmic microwave background radiation fills all space witha.dpeli:3 aa5 an average energy densitpal.a 35adi:ey 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 +83sldy +or9tor b/4sa7i -v+kgyy hp in the sunlight that hits Mars, knowing that the Earth receives abouv+pk49t8oor s-r+sl7+a ihgb/y y3ydt $1350\mathrm{~W/m^2}$ 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 h ( aogmkv2*8rkd1-baxl/h 5r mave its maximum magnetic field pointing west and its maximum electric field pointing south. In which di b/k8 aa*vk xdghm5-m21orl (rrection 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 w-5e g nli/,jt;lkwb2f ere
(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 i 8xad 7*5qaoethat consists of a 380-loop circular coil of wireiax o8a7 q5de* 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 sigrb u5n4+ s/rbfnal 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, theh zgp0 eu5s5iz iq1n(hs;9x sv/0jk s: amplitude of the electric field is :xqs1us50ii5; (egsz0 vnkh9 hsjp/ z$0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitance of a radio tuner consisttup( (4bldb6c s of six plates connected together placed alternately between six other platbup(d(bl tc64es, 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 av(dx rv21h j7oxerage 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 energyytd 0n0 pxhi,yn/)b-i uniformly in all directions at an average rate i/dyy0b x,0npt h-n i)$P_0$ 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 n(r xw- b,foht3j zfuc2fb7y j-;d*(o station 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 distance of 100 km from the stationq292 ;bn:hf x.abyrzf.
(a)    $\mu W$
(b)    V/m
(c)    V

  What is the maximum y.n /1krgnk 7ypower level of 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 antenna is a point source. Air brgn1 7.ryk/ knyeaks down in an electric field of about $3\times10^6\mathrm{~V/m}.$ [Hint: See Problem 51.]    $\times10^{11}\mathrm{W}$