近日,海南某高校大二学生小李向本报记者反映,英语四六级考试是全国统考,但各省报名费不同。“河北报考英语四六级考试的费用才25元。”小李说,而海南省的英语四六级报名费是40元,这是什么原因?

2013年英语六级听力练习:隧道与广播

海口网 http://www.hkwb.net  时间:2013-03-22 14:37

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

为什么在隧道中调频广播比调幅广播的信号要好一点?

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.

这是因为调频广播台的传播频率要频繁些。通常在88到108兆赫。即每秒转1亿圈。

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,调频广播电台发出的一个电波的长度只有几米,大概是一辆车的大小。而调幅广播站发出的电波长达几百米。

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.

在穿越隧道时,长的波长会被吞并阻碍。而来自调频广播高能量,波长又短的电波则不会被吞并或阻碍。相反的,它们会被隧道表面反射回来。

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.

当然,它们只会在某个区域内反弹。如果隧道太长的话,即使是调频广播也会逐渐变弱直到驶出隧道。

海口网 http://www.hkwb.net [来源: 考试吧Exam8.com] [作者:] [编辑:韩静] 

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