radio and telephone is that radio uses no electrical signals which
travel long distances along wires. Instead invisible waves, moving
at the same speed as electrical signals, are used. A few years ago
there were not many radio stations in the world. Today there are
many hundreds of radio stations broadcasting in different languages
and in all countries. The invisible radio waves can easily travel
from one country to another. This means that listeners in one
country can listen to programmes broadcast from another country. In
this way information travels from country to country. Radio is often
used by policemen to communicate with one another. In addition,
police forces in one country can communicate with those in other
countries in order to catch criminals. Ships at sea use radio so
that they know exactly where they are. Aeroplanes use radio for the
same reason and this makes it easier for them to find their way from
place to place.
In the modern world there are many methods of communication. As well
as radio there is television, for example. This enables information
in the form of a picture to be broadcast from one place to another.
Radio is often used as part of a telegraph system where distances
are very large. Of the many modern methods of communication, radio
probably remains the most important.
2. How the Program Is Broadcast?
We turn on the radio and a program comes to us from a
broadcasting station miles and miles away. We know that words and
music themselves haven’t traveled all that distance through space,
上一页 [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] 下一页
Tag:高二英语教案，高二英语教案模板，教案大全 - 英语教案 - 高二英语教案