时差N小时:穿越隧道 Driving through a tunnel
唐:多么适合兜风的天气!你觉得我的新法拉利怎么样?
Yael:Very fancy.
雅艾尔: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,收音机也很酷,所以我们仍然可以享受科学时刻节目。
Hey, I think it's coming on now.
嘿,我想节目马上就来了。
Yael:Hey, where'd the signal go?
雅艾尔:嘿,信号去哪里了?
Don:It must be because we're driving through a tunnel. Try an FM station.
唐:那一定是因为我们开车穿过一个隧道的缘故。试试一个FM调频电台。
Yael:There it is!
雅艾尔:有了!
How come we can hear FM longer in a tunnel than AM?
为什么我们在隧道中能听到FM调频而不是AM调幅?
Don:It's because FM stations transmit at higher frequencies.
唐:这是因为FM调频电台传输更高的频率。
They generally go from eighty-eight to one-hundred-and-eight megahertz.
通常会从88到108兆赫。
That's over a hundred million cycles per second.
超过每秒一亿次。
Yael:Wow! That's pretty fast.
雅艾尔:哇!那可是相当快。
Don:As a result, a single radio wave from an FM station is only a few meters long, about thesize of a car.
唐:结果, FM电台单一的无线电波只有几米长,约相当于一辆车。
An AM station is putting out radio waves that are hundreds of times as long!
而AM电台伸展数百倍长的无线电波!
Yael:So the longer wavelengths can't make it as easily into tunnels?
雅艾尔:那长的电波不是更容易进入隧道吗?
Don:Long wavelengths tend to be absorbed or blocked as they try to enter the smallertunnel.
唐:长电波在试图进入较小的隧道时往往被吸收或阻碍。
The higher-energy and shorter-wavelength waves from an FM station aren't absorbed orblocked as much.
而FM电台的高能量和短波长电波没有被吸收或阻碍。
Instead, they tend to bounce around and get reflected off of surfaces.
相反,它们被从表面反弹和反射。
Yael:Like the inside of a tunnel.
雅艾尔:像是隧道里。
Don:Yep. Of course, they only bounce so far.
唐:是的。当然,它们只是反弹到这段。
If the tunnel is long enough, even FM stations fade out until you come out the other end.
如果隧道足够长,甚至直到你从隧道另一端出来FM电台也会渐渐弱化。
Yael:Here we are!
雅艾尔:我们现在就出来了!
