问题 单项选择题

X线摄影中,使胶片产生灰雾的主要原因是()

A.相干散射

B.光电效应

C.光核反应

D.电子对效应

E.康普顿效应

答案

参考答案:E

解析:在X线摄影时,从X线球管中发出的射线束可以作用于辐射场内的任何物体,包括待检肢体及其他部位:暗盒、摄影床(架)、墙壁、地板等,发生光电吸收、康普顿效应、散射、反射等,一方面可以使胶片感光最终形成影像;另一方面,也产生了大量散射线,若其作用于胶片则形成照片灰雾,而且散射线越多灰雾越大。

填空题

动词填空。阅读下面短文,用括号内所给动词的适当形式填空 (必要时可加情态动词或助动词)。

    My grandmother was an iron-willed (强硬的) woman. When I was five, she invited some friends to her

apartment. Among the guests there (1)_____ (be) a rich man and his daughter. Grandmother considered them

the most important among the guests.

    During the party, I went to the bathroom. I was still sitting down when the girl walked in. "You (2)____

(stay) here too long!"  

    It's not your business. Don't you know that little girls shouldn't come into the bathroom when a little boy

(3)_____ (use) it!?" I said in anger. This (4)______ (surprise) the little girl. Then she started to cry. Most guests

had heard what I said and laughed. But not Grandmother.

    She (5)______ (wait) for me when I left the bathroom. Grandmother shouted that I was impolite and rude

and ordered, "You (6)_____ (say) sorry to her." All the guests watched in silence.

    Twenty minutes later, Grandmother walked by the bathroom and noticed a torrent (激流) of water (7)____

(run) out from under the door. Everyone knew who did that. Grandmother was so angry that she tried (8)_____

(get) me anyway. It took several strong men finally to move her away and calm her down.

    My grandfather took me by the hand and seated me on his lap. He looked at me, not at all angry or upset.

"(9)_____ (tell) me," he asked, "why did you do it?" 

    "Well, she shouted at me for nothing," I said seriously. "Now she's got something to be angry at." 

    Grandfather didn't speak right away. He just sat there, looking at me and smiling. I (10)______ never _____

(forget) his expressions (表情) for my whole life. 

    "Eric," he said at last, "I think you did the right thing."

单项选择题