问题 单项选择题

发光二极管的核心部分是由p型半导体和n型半导体组成的晶片,在p型半导体和n型半导体之间有一个过渡层,称为PN结。在某些半导体材料的PN结中,注入的少数载流子与多数载流子复合时会把多余的能量以光的形式释放出来,从而把电能直接转换为光能。PN结加反向电压,少数载流子难以注入,故不发光。这种利用注入式电致发光原理制作的二极管叫发光二极管,通称LED。当它处于正向工作状态时(即两端加上正向电压),电流从LED阳极流向阴极时,半导体晶体就发出从紫外到红外不同颜色的光线,光的强弱与电流有关。
对文段理解不正确的是______。

A.LED能发光是利用注入式电能转化成光能的技术
B.发光二极管是由p型半导体、n型半导体和PN结组成
C.PN结位于p型半导体和n型半导体的过渡层上
D.LED的状态是通过PN结外加电压来控制的

答案

参考答案:B

解析: 本题考查的是对文段细节的把握。B项论述错误,对应原文第一句话可知,p型半导体和n型半导体组成的晶片仅是发光二极管的核心部分,而不是发光二极管。

选择题
阅读理解

For many people in the US,sports are not just for fun. They’re almost a “religion”.Thousands of sports fans buy expensive tickets to watch their favorite teams and athletes play in person .Other fans watch the games at home,sticking to their TV sets,never missing a game. Many a wife becomes a “sports widow” during her husband’s favorite season. Americans’ devotion to sports has created a new class:professional athletes. Sports stars often receive million­dollar salaries. Some even make big money by appearing in advertisements for soft drinks,shoes and almost everything.

Sports are an important part of American culture. Throughout their school life,Americans learn to play many sports. Many students try out for the school teams. Athletic events at universities attract scores of fans and benefit the whole community. Many people also enjoy non­competitive activities,like hiking,cycling,horseback riding,camping or hunting.

Many sports were imported from other countries. Europeans brought tennis,golf,bowling and boxing to America .Football and baseball came from other Old World games. Only basketball has a truly American origin. Americans export sports fever as well. Satellites broadcast games to sports fans around the globe. NBA is a good example. The names of American superstars like basketball great Michael Jordan have become household words all over the world.

小题1:.Many a wife becomes a “sports widow” in the US probably because________.

A.they are serious in religion

B.they are devoted to sports

C.their husbands stick to sports

D.their husbands are missing小题2:.Which of the following is NOT true according to the passage?

A.The US sports stars can earn a large sum of money via the media.

B.American students go in for various sports and athletic events.

C.Lots of American people take part in non­competitive activities.

D.American people like to exchange different sports from each other.小题3:.The writer mainly intends to tell us________.

A.how important sports are in America

B.where sports can help to make money

C.why sports are so popular in America

D.what affect Americans’ everyday life