β+粒子与物质作用耗尽动能后，将与物质中的电子结合，正负电荷相互抵消，两个电子的质量转换为两个方向相反、能量各为0.511MeV的γ光子。这个过程被称为（）
A.湮灭辐射
B.轫致辐射
C.弹性散射
D.激发
E.光电效应
参考答案：A
解析：湮灭辐射是指β粒子与物质作用耗尽动能后，将与物质中的电子结合，正负电荷相互抵消，两个电子的质量转换为两个方向相反、能量各为0.511MeV的γ光子。
| 阅读理解。 | ||
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| 1. How many bedrooms are there on the second floor of the house? | ||
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| A. Four. B. Five. C. Six. D. Seven. | ||
| 2. Which is NOT true about the house? | ||
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| A. It has a garden around it. B. It is by the beach. C. It is by a busy street. D. It is large. | ||
| 3. Which is TRUE about the apartment? | ||
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| A. It is good for a big family. B. It is in a city. C. It is in an old building. D. It has a beautiful garden. | ||
| 4. If you want to see the house, how could you see inside of it? | ||
[ ] | ||
| A. Call Jim and he will show you. B. Ask people living there to show you. C. Go there. The door is open. D. You can only see pictures. | ||
| 5. What does it mean if you are "eager" to do something? | ||
[ ] | ||
| A. You are careful doing it. B. You must do it. C. You often do it. D. You want to do it very much. |