时间:2019-02-15 作者:英语课 分类:英语时差8,16


英语课

 Have you even wondered why you can hear FM radio signals in a tunnel longer than AM? Take a ride with Don and Ya?l to find out why.   D: What a great day for a drive! How do you like my new Ferarri?


Y: Very fancy.
D: Best of all, the radio works, so we can still enjoy A Moment of Science. Hey, I think it's coming on now.
[SOUNDS]
Y: Hey, where'd the signal go?
D: It must be because we're driving through a tunnel. Try an FM station.
[SOUNDS]
Y: There it is!
[SOUNDS]
How come we can hear FM longer in a tunnel than AM?
D: It's because FM stations transmit at higher frequencies. They generally go from eighty-eight to one-hundred-and-eight megahertz. That's over a hundred million cycles per second.
Y: Wow! That's pretty fast.
D: As a result, a single radio wave from an FM station is only a few meters long, about the size of a car. An AM station is putting out radio waves that are hundreds of times as long!
Y: So the longer wavelengths 1 can't make it as easily into tunnels?
D: Long wavelengths tend to be absorbed or blocked as they try to enter the smaller tunnel. The higher-energy and shorter-wavelength waves from an FM station aren't absorbed or blocked as much. Instead, they tend to bounce around and get reflected off of surfaces.
Y: Like the inside of a tunnel.
D: Yep. Of course, they only bounce so far. If the tunnel is long enough, even FM stations fade out until you come out the other end.
Y: Here we are!
 

n.波长( wavelength的名词复数 );具有相同的/不同的思路;合拍;不合拍
  • I find him difficult to talk to—we're on completely different wavelengths. 我没法和他谈话,因为我们俩完全不对路。 来自《简明英汉词典》
  • Sunlight consists of different wavelengths of radiation. 阳光由几种不同波长的射线组成。 来自辞典例句
学英语单词
abnormal termination abort
Acomatacarus major
allantoicase
amoureuse
antifoundational
banausic
bathurst
Blerick
bracket light
car mirror
centre of dispersal
cepheid variables
ceramic DIP
chamazulenogene
chloranilate
circuit tester
coeruleum thymolis
coordiator
copyright infringement
cortex granati
cosyntropin
counter-clockwise angle
court trusts
cover type map
cupressus arizonicas
cylinder band
declaimeth
deener
dense-graded asphalt concrete
Deutzia nanchuanensis
diesel reduction drive
different diameter roll type husker
distribution account of national income
double-occupancy
draw beam
dustbathing
enprisoning
fitted value
fractional digit
gastricisin
georg ohm
goatburger
guinea keets
Herzegowina
high muckety-muck
Hopf mapping
hypoventilating
Ijesa-Tedo
infrahepatic
kerin
macphersonite
matrimony vines
memorialis hirta (bl.) wedd.
metallic hydrogen
milk tanker transporter
miniseriess
misrepresentation of health information
mother-fuckers
mountain-making movement
neon filledtube
Ness, River
objective analysis value
Oosterdijk
opening of the telescope
overall logic
pearl knitting
periaqueduct
policy credibility
polychromatic light
potassium cobalto-nitrite
Potentilla nervosa
powdered vulcanized rubber
Przysucha
recovery process
red flower
rediverted
relapseth
retroarcs
rexman
Ruhinda
saddle friction-plates
second-string
single-speeds
stealings
stop valve spindle
structural component
supmmeatai triangle
thermal initiation
thermal underwears
topographic interpretation
trapezium segment
trial-for-ignition period
UKBA
umbworld
unbind
uniquely defining class
vehide currency
veiniest
wasn't
witnessest
xenogenesis
Yagi-Uda array