The electric field in an EM wave r5 cag xuwhgt0m)* 8)wtraveling north oscillates in an east–west plane. Describe the direction of the magnetic field vegxm8rwg 5*0ct) )huawctor in this wave.

Is sound an electromagnetic wave? If not, what kixy)jz.rh h8lk zp7fkx kh3f;i55ca- n1q2p a,nd of wave is it?

Can EM waves travel t95m83fkah gb9wv1/ /ger qp9d *dh fxahrough a perfect vacuum? Can sound waves?

When you flip a light switch on, does the light go on immediately? Exn fvouu * t/it:hir(6/plain.

Are the wavelengths of radio and tel(mw1-rq8kh rce 9fk ,gevision signals longer or shorter than those dete,h1rmk 8fk (e 9wr-gqcctable by the human eye?

When you connect two loudspeakers vec/8m r11ko;ab0 uthto the output 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 mu av8r1k1 te/h0obc; between speakers? Explain.

In the electromagnetic spectrum, what type of 5-bv mw3 asw mx*8e3yiEM wave would have a wavelength ofs bmy-xw53wvm* 83e ia $10^3km$ 1 km? 1 m? 1 cm? 1 mm? $1\mu m$

Can radio waves have the same frequencies as sound waves ( yzn:4:* 9k0awzkm+h-t. paap0tqjag 20 Hz–20,000 Hz)?

Can two radio or TV stations brpcg)vvxp -u(3wmss1yf)-u6ml in u) 5 oadcast on the same carrier frequency? Explain.

If a radio transmitter has a verup3um t/ uzv3vpt fz3+4:kp+ewg 4bm:tical antenna, should a receiver’s antenna (rod type)+wez3pt 4:fgu4 v+m 3/p vkzmubtup:3 be vertical or horizontal to obtain best reception?

The carrier frequencies of FM broa4 y*nh ,/4fyl(l-y l i07(uarqj u htlw4baj,mdcasts are much higher than for AM broadcasts. On ,jtym(iu 40rq j,-ll4n7abahlyf(/hylw4 * u 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 buildings.

Discuss how cordless telephones make use of EM w(.v(0sd ;y2cgz xuhd/j lbl3d aves. What about cell phones?

A lost person may signal by flashing a flashlight on and off using Morse code.x8.gglzk1nwi;w 85 c. aj say7 g-,moc This is actually a modulated EM wave. Is it AM or FM? What is the frequency of n - x78.jmogagc k1.8gyiszal,;5wcwthe carrier, approximately?

  At a given instant, a 1.8-A current flows in the wires connected to a parallel-pe1l pgjy6-0no 6zqe w,late capacitor. What is the rate at which the electric field is changing between the plates if the square plates arew1e6z06,pj-qng y elo 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 mayl6cz gg -0 k(ps0yjg+gnitude 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 vertically and habb yd1nj k;);cs a frequeck; j1;bdn y)bncy 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 frequency of a microwave whose wavelength is 1zzb9 ct; n5tj7.60 $cm$?    $ \times10^{10}\mathrm{Hz}$

  What is the wavelengtoki)2b-ahnn+ 90mq bz h of a $29.75\times10^9-Hz$ radar signal?    $ \times10^{-2}\mathrm{m}$

  An EM wave has freques ;lwy*zx x23v(5xcyi +a8v ((d qw+mdmdv3rdncy $9.66\times10^{14}\mathrm{~Hz}.$ What is its wavelength, and how would we classify it?    nm

  An EM wave has a wavelen gr:e-j-5ka hqgth 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 lizxtrs/ c5mf1 e:/jh5fvvqs42ght to reach us from the Sun, $1.50\times10^8\mathrm{~km}$ away?    min

  A widely used “short-wave” radio broadcast-8 pu:v lku+ie band is referred to as the 49-m band. What is the frequency of a 49-8kvi uup+:el -m radio signal?    $ \times10^{6}\mathrm{Hz}$

  Our nearest star (other than the Sun) is 4.2 light-years whh+9h 80ac*ey;cvwgvvjjbr 6wl6 8,away. That is, it takes 4.2 years for the light it emits to reach Earth. How far away l*8g , jhv 8+yv;br wjweca9cw 60hhv6is it in meters?    $\times10^{16}\mathrm{m}$

  A light-year is a measure of distance (not time). How many meters does lig5 vn iwh9e vp(oom 2d+l.b5c8oht travel in a yeaw b5( eo+ vpdh8o2 cv5nl.9iomr?    $ \times10^{15}\mathrm{m}$

  How long would it take a message sent asbm2l2vh3 c/yn 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 light-speed experiment to a size that p47,h k( rhs,cz vz9-ze8pfs uwill fit in one room. A six-sided mirror is available, and the stationary mirror can be mounteur,9(h7 e 4 v8kspzps-fzhc, zd 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 — a person in the balcony 50 hau th62+oblqih*l6 t35qr0j.0 m away from the stage (Fig. Below), or a person ujht+oatqqr6*hil 02b36 l h 53000 $km$ 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 inf6b* 4fkk(drwy2ot ;zb+y 3zq science and medicine produce very short bursts of electromagnetic enery4kb+ t db3*fy (2zowk6fr;zqgy. 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 sl 2zi2l yg0ajp. gbw /ekpwemp;:)k+(trength 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 transpo)4lhezsm2plty9o q(,a 1 tuf,rted 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 distance ofd1utbq 9 8swi x9.puvhle7f 1( 10.0 m, what is the average inten dtp89wui1q7 f h. lbuvx1se(9sity, 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 outputd,v1efkhj07n nau.y)u1u20)z lj kw m 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 is g6xh72: yo ,u zqmvbx8$2.5\times10^{-7}\mathrm{~Т},$
(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 ofuq, m35czhv8m 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 radiatiq:4sue jin4*3gkv jlb12w2yzkz6.p zon pressure 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 wavei( ic ydqu9(-wlengths 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 recepu 0 r*r*e1jvjc2 rno8xtion.    m

  Compare 940 on the AM dial to 94 on the FM dial. Which has theabdau 6q+0tbwvhu+(* longer wavelength, and by what q a buvb6+dh*0(ta+wu factor is it larger?
 ----待选择----AMFM 
$\frac{\lambda_1}{\lambda_2}$ =   

  What are the wavelengths forn- lli)t0b:fzvj 5b3x two TV channels that broadcast at 54.0 MHz (Channel 2) an:zj0 i lvbx)f-nlt b53d 806 MHz (Channel 69)?
$\lambda_2$ =    m
$\lambda_{69}$ =    m

  The variable capacitor in the tuner of an AM radio has a capacitance of 2800ert6/ +s * msv8rigz*k $pF$ 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 96.14j6gcu) htp 5d+f2p+r+aalg a -$MHz$ FM station has an inductance of $1.8\mathrm{~}\mu\mathrm{H}.$ What value must the capacitance be?    $pF$

  A certain FM radio tunin+9e4kci3qoc n g circuit 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 receiver that cand jy l*:1tvo3:eab 2l:le/v ny tune a range from 14b3alj1 lye *l :2 ty::/ovednv.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 radiaw :r./d0zvdf5r 0khyo di-( yntion 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 paralleop yk:eoi6w+4 fcn 4s9l to the electric field of an EM wave. How large must the electric field be to pyi es4:k6n+ofo9 pw4croduce 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 outp1g3ch4pgyb6y)c jtf 9j8 w 5ajut, how long would it take for us on Earth to lear b13 jgc95 a4y8cpyfth6jw j)gn about it?    min

  Light is emitted from an ordinary lightbulb fi*x1e-b*lybx klament in wave-train bursts about -1*xyb* kexlb$10^{-8}\mathrm{~s}$ 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 the9zjft2: py e4w first astronauts on thyf 4wp2je:zt 9e 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) was b/phpoe 7ke yw 1.2axhxh(y42meamed to a listening crowd from a radio speaker. If you were standing 25 m from the loudspeaker, what was the total time lag between whenmp oe/2y 2xaw(yhk47hx .1eph you heard the sound and when the sound left the Moon?    s

  Cosmic microwave background radiation fills all space with an average energy 2-bew:f + wohaden -+ohawew b2:fsity 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 thavve *c9tp 8kp4t the Earthk9t4c 8*pepv v 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 tim: p8 uu//hihdv c2a hk5go8/lbe, a traveling EM wave is noted to have its maximum magnetic field pointing west ai 5ul8bc/o g /h2da:uv/ 8hkhpnd 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 if it4ww5.( b.ipw)g( 8fxoxag apb49flm4d ogul6 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 (rmsy3t: li r mp(c7nlc vfca/ye5m/a(n 16) will be generated in an antenna that consists of a 380-loop circular coil ol 3mtaa/7(mp 6ynev1yl fi 5cc(:rc/ nf 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 particularfb( on,ee;6 sv 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 of the electm ;p vkgv/ 6xr*dpon72ric field 6knvp27x/;o*grd p m vis $0.12\mathrm\,{~V/m}.$ What is the average power output of the radio station?    $kW$

  The variable capacitance of a radio tuner consists of six plates connected togetsszw.l9(1k-rb qas eic3w- 6f her placed alternately between six other plates, also connected together (Figfis(36z -wbsscea .q-r 9w1k l. 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 k.+6,bfo d(p fn vd*3q26)jmbt spspa; m-ljd 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 averagemj 5cci ,5d65q9xxrm e ratec65medx 9i cm55xqj,r $P_0$ 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 sto0gc*:))z tp uk9zbxbation 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 di7 y7 *xizyq/wlu ke9u5ba3f 3h4/neoustance 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-dqf-; fnw/ 2s:*jr:igh4shqba5w xx 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 breaks down in an electric field of abo*q;2ais:q- w:xhj/r gs4b5-fhfw ndxut $3\times10^6\mathrm{~V/m}.$ [Hint: See Problem 51.]    $\times10^{11}\mathrm{W}$