時(shí)差N小時(shí):穿越隧道 Driving through a tunnel
唐:多么適合兜風(fēng)的天氣!你覺得我的新法拉利怎么樣?
Yael:Very fancy.
雅艾爾:非常花俏。
Don:Best of all, the radio works, so we can still enjoyA Moment of Science.
唐:最重要的是,收音機(jī)也很酷,所以我們?nèi)匀豢梢韵硎芸茖W(xué)時(shí)刻節(jié)目。
Hey, I think it's coming on now.
嘿,我想節(jié)目馬上就來了。
Yael:Hey, where'd the signal go?
雅艾爾:嘿,信號(hào)去哪里了?
Don:It must be because we're driving through a tunnel. Try an FM station.
唐:那一定是因?yàn)槲覀冮_車穿過一個(gè)隧道的緣故。試試一個(gè)FM調(diào)頻電臺(tái)。
Yael:There it is!
雅艾爾:有了!
How come we can hear FM longer in a tunnel than AM?
為什么我們?cè)谒淼乐心苈牭紽M調(diào)頻而不是AM調(diào)幅?
Don:It's because FM stations transmit at higher frequencies.
唐:這是因?yàn)镕M調(diào)頻電臺(tái)傳輸更高的頻率。
They generally go from eighty-eight to one-hundred-and-eight megahertz.
通常會(huì)從88到108兆赫。
That's over a hundred million cycles per second.
超過每秒一億次。
Yael:Wow! That's pretty fast.
雅艾爾:哇!那可是相當(dāng)快。
Don:As a result, a single radio wave from an FM station is only a few meters long, about thesize of a car.
唐:結(jié)果, FM電臺(tái)單一的無線電波只有幾米長(zhǎng),約相當(dāng)于一輛車。
An AM station is putting out radio waves that are hundreds of times as long!
而AM電臺(tái)伸展數(shù)百倍長(zhǎng)的無線電波!
Yael:So the longer wavelengths can't make it as easily into tunnels?
雅艾爾:那長(zhǎng)的電波不是更容易進(jìn)入隧道嗎?
Don:Long wavelengths tend to be absorbed or blocked as they try to enter the smallertunnel.
唐:長(zhǎng)電波在試圖進(jìn)入較小的隧道時(shí)往往被吸收或阻礙。
The higher-energy and shorter-wavelength waves from an FM station aren't absorbed orblocked as much.
而FM電臺(tái)的高能量和短波長(zhǎng)電波沒有被吸收或阻礙。
Instead, they tend to bounce around and get reflected off of surfaces.
相反,它們被從表面反彈和反射。
Yael:Like the inside of a tunnel.
雅艾爾:像是隧道里。
Don:Yep. Of course, they only bounce so far.
唐:是的。當(dāng)然,它們只是反彈到這段。
If the tunnel is long enough, even FM stations fade out until you come out the other end.
如果隧道足夠長(zhǎng),甚至直到你從隧道另一端出來FM電臺(tái)也會(huì)漸漸弱化。
Yael:Here we are!
雅艾爾:我們現(xiàn)在就出來了!
