Add text-based questions to the given ones and answer them

1. What does the word “semiconductor” mean in present-day electronics?

2. Where does silicon appear?

3. What does elemental form of silicon mean?

4. What is single crystal form?

5. How is high-purity silicon specified?

6. Why are impurities added to silicon?

7. Why is the manner in which conductivity is altered important?

8. …

9. …

10. …

SPEAKING

Summarize the text “Intrinsic Silicon” in 250 words using the questions of ex.12 as a plan.

Divide into 2 groups. Group 1 translates extract A group 2 translates extract B of the text “Communicating Through the Earth” with a dictionary in writing.

Extract A

How do we communicate with people beyond the horizon? What can be made to follow the curve of earth's surface?

Of course, we can send electrical signals through wires around any curves. In the nineteenth century, copper wires were strung across the continents and ocean floors and the world was united through te­legraphy. That takes a lot of copper, though, and a lot of maintenance.

We could send light-wave signals and do away with wires, but light waves move in a straight line and won't curve around the earth's bulge. We would have to set up relay stations or place mirrors in orbit to make that work.

Radio waves, like light waves but a million times longer, do better. They travel in straight lines, too, but the upper atmosphere contains regions rich in charged particles (the ionosphere) that tend to reflect radio waves. It is as though there were natural mirrors in the sky. That makes it possible to send radio signals to long distances, and in the twentieth century the world was united without wires.

However, the ionosphere is affected by the solar wind. When the sun produces flares, an electrical storm can take place that will disrupt radio communications.

But short radio waves (microwaves) can go right through the ionosphere and be amplified and sent on by communications satellites. As communications satellites improve, signals will be sent from place to place on the Earth with so little trouble that it would seem unreasonable to ask for anything better.

What can go through the Earth itself? Light certainly can't. Radio waves can't. We can't even string wires through the Earth to carry electrical signals.

One thing that does travel through the body of the Earth is an earthquake wave, but it takes a very hard blow to set the Earth to vibrating perceptibly.