時差N小時:穿越隧道 Driving through a tunnel

Don:What a great day for a drive! How do you likemy new Ferarri?

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,收音機也很酷,所以我們?nèi)匀豢梢韵硎芸茖W(xué)時刻節(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:那一定是因為我們開車穿過一個隧道的緣故。試試一個FM調(diào)頻電臺。

Yael:There it is!

雅艾爾:有了!

How come we can hear FM longer in a tunnel than AM?

為什么我們在隧道中能聽到FM調(diào)頻而不是AM調(diào)幅?

Don:It's because FM stations transmit at higher frequencies.

唐:這是因為FM調(diào)頻電臺傳輸更高的頻率。

They generally go from eighty-eight to one-hundred-and-eight megahertz.

通常會從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電臺單一的無線電波只有幾米長,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電臺伸展數(shù)百倍長的無線電波!

Yael:So the longer wavelengths can't make it as easily into tunnels?

雅艾爾:那長的電波不是更容易進入隧道嗎?

Don:Long wavelengths tend to be absorbed or blocked as they try to enter the smallertunnel.

唐:長電波在試圖進入較小的隧道時往往被吸收或阻礙。

The higher-energy and shorter-wavelength waves from an FM station aren't absorbed orblocked as much.

而FM電臺的高能量和短波長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,甚至直到你從隧道另一端出來FM電臺也會漸漸弱化。

Yael:Here we are!

雅艾爾:我們現(xiàn)在就出來了!