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近日,海南某高校大二學(xué)生小李向本報記者反映,英語四六級考試是全國統(tǒng)考,但各省報名費(fèi)不同?!昂颖眻罂加⒄Z四六級考試的費(fèi)用才25元?!毙±钫f,而海南省的英語四六級報名費(fèi)是40元,這是什么原因?

2013年英語六級聽力練習(xí):隧道與廣播

??诰W(wǎng) http://mmkcvlj.cn  時間:2013-03-22 14:37

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

為什么在隧道中調(diào)頻廣播比調(diào)幅廣播的信號要好一點(diǎn)?

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.

這是因?yàn)檎{(diào)頻廣播臺的傳播頻率要頻繁些。通常在88到108兆赫。即每秒轉(zhuǎn)1億圈。

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!

因此,調(diào)頻廣播電臺發(fā)出的一個電波的長度只有幾米,大概是一輛車的大小。而調(diào)幅廣播站發(fā)出的電波長達(dá)幾百米。

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, much like the inside of a tunnel.

在穿越隧道時,長的波長會被吞并阻礙。而來自調(diào)頻廣播高能量,波長又短的電波則不會被吞并或阻礙。相反的,它們會被隧道表面反射回來。

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.

當(dāng)然,它們只會在某個區(qū)域內(nèi)反彈。如果隧道太長的話,即使是調(diào)頻廣播也會逐漸變?nèi)踔钡今偝鏊淼馈?/p>

??诰W(wǎng) http://mmkcvlj.cn [來源: 考試吧Exam8.com] [作者:] [編輯:韓靜] 

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