问题 单项选择题 A1/A2型题

能量80keV的电子入射到X射线管的钨靶上产生的结果是()

A.连续X射线的最大能量是80keV

B.特征X射线的最大能量是80keV

C.产生的X射线绝大部分是特征X射线

D.仅有1%的电子能量以热量的形式沉积在钨靶中

E.以上都是

答案

参考答案:A

解析:特征X射线的能量与靶原子壳层的结合能有关;X射线的两种成分中,特征X射线只占很少一部分;绝大部分的电子能量变为了热能。

阅读理解

阅读下面短文,判断下列句子的正误,正确的用“A”表示,错误的用“B”表示。

     Who wants to carry a heavy bag to school? Not children. Nobody wants one shoulder to be lower than the other, and aching too. In India,  most people would look at the reduction(减少) of textbooks as a way out.  But in a country like America, there are always more choices. A company called goReader has created a "school bag" which is  as  small  as  a  laptop  computer (笔记本电脑) ,  weighing . about 2.5 kg. The goReader has a color screen and can "hold" any textbook that a student may need, says a report in The Asian. Age Newspaper.      

     The company plans to work closely with the publishers(出版社) of textbooks so that these books can be offered on the Internet.  All the students will have to do is to download(下载)  their textbooks.  Making notes and marking key parts of a lesson can be done just as students have usually done on their textbooks.      

     At present, the project is being tested out in a university.  Richard, who founded. the company, is having his invention tested at Chicago's DePaul University, where he studied. Does that mean we will say gooLlbye to the soimd of tuming ne,w paper and the smell of  the black ink?  

( )1. Children like to carry heavy bags to school according to the passage.  

( )2.  The school bag created by goReader is very big and heavy.  

( )3. There are many kinds of textbooks in goReader.  

(    )4. Students can't make notes and mark key parts of a lesson on the school bag created by goReader at present.  

( )5. Richard graduated from Chicago's DePaul University.

选择题