问题 单项选择题

高速运行的电子将靶物质原子中某层轨道电子击脱,形成空穴。此时,外层(高能级)轨道电子向内层(低能级)空穴跃迁,释放能量,产生X线。X线的波长由跃迁电子能量差决定,与高速运行电子的能量无关。高速电子的能量可决定能够击脱某壳层的电子。管电压在70kVp以下时,电子产生的动能不能把钨靶原子的K壳层电子击脱。

下列叙述错误的是

A.高速电子与靶物质轨道电子作用的结果

B.X线的质与高速电子的能量有关

C.X线的波长由跃迁的电子能量差决定

D.靶物质原子序数较高的X线的能量大

E.70kVp以下钨靶不产生

答案

参考答案:B

阅读理解

This was no ordinary class. The students who came together were all science or engineering professors at Cornell University. They had interrupted their research to accept an invitation to take part in an unusual experiment: “an interesting week of poetry.” This class was part of a study to answer the questions: Why is science difficult for many nonscience students? What can teachers learn about teaching if they take a class that is not in their field?

The students in the poetry class listened to lectures and took notes. They had reading tasks and had to write three short papers. All students noticed one thing – the importance of spoken words. In science and engineering classes, the instructors put tables and drawings on the blackboard. But in this poetry class, the instructors just talked. They didn’t write anything on the board.

The scientists and engineers noticed one similarity between science and poetry. In both subjects, students need to find layers (层次) of meaning . Some layers are simple, clean, and on the surface; other layers are deeper and more difficult. This search for different levels of meaning doesn’t happen much in undergraduate(本科) science classes, but it is important later, in graduate school. And it is always important in humanities(人文科学).

Both the poetry instructors and their students learned something about teaching from this experience. One poetry instructor, for example, now sees the importance of using informative as he teaches. Most of the scientists agreed on several points. First, humanities classes might help science students to see patterns and decide which information is important. Second, the poetry class was fun. One engineer decided, “We need to change the way we teach engineering to make to make it an enjoyable experience for students.”

But perhaps the most important result of the experience was this; All of the professors began to think about how they teach and how they cam teach better.

小题1:What do we know about this unusual class?

A.The teachers did lots of writing on the board

B.The teacher were invited to attend several lectures.

C.The student were professors from a university

D.The students were studying science and humanities.小题2:The experiment was designed to find out             

A.how to teach the students in the science class

B.whether poetry is difficult for science students

C.what to be taught in the humanities class

D.why many humanities students find science hard.小题3:Finding levels of meaning is            .

A.important for graduate students in humanities

B.difficult for graduate students in humanities

C.common for undergraduate students in science

D.easy for undergraduate students in science.小题4:What did the science professors learn after the experiment?

A.They should change the way they teach

B.A poem could be explained in clear definitions.

C.A poetry class could be more informative.

D.Their teaching was an enjoyable experience.

名词解释