问题 选择题

扫描隧道显微镜(STM)是根据量子力学原理中的隧道效应而设计成的,当原子尺度的探针针尖在不到一个纳米的高度上扫描样品时,外加一电压(2mV~2V),针尖与样品之间产生隧道效应而有电子逸出,形成隧道电流.电流强度随针尖与样品间的距离的减少而指数上升(如图1所示),当探针沿物质表面按给定高度扫描时,因样品表面原子凹凸不平,使探针与物质表面间的距离不断发生改变,从而引起隧道电流不断发生改变.将电流的这种改变图象化即可显示出原子水平的凹凸形态.扫描隧道显微镜的分辨率很高,横向为0.1~0.2nm,纵向可达0.001nm.如果探针针尖在图2所示的样品表面,从图示位置开始,以恒定高度做一维匀速扫描,如果针尖与样品间地距离在r1和r2的范围内变化,则产生的隧道电流可能是选项中的哪种?(  )

A.

B.

C.

D.

答案

由题意,探针针尖在图2所示的样品表面以恒定高度做一维匀速扫描,在一个周期内:前半个周期,探针针尖与样品间的距离均匀增大,由图(1)知,隧道电流非均匀减小,在后半个内,探针针尖与样品间的距离均匀减小,由图(1)知,隧道电流非均匀增大,故C正确.

故选C

单项选择题 A2型题
写作题

近期, 你所在城市的中学生就“最美汉字”进行投票。请阅读下面一则新闻报道, 用英文写一篇短文, 向学校英文报“Happy Teens”专栏投稿。

High school students recommend ren as message to the world

The Chinese character ren, a word that generally means “benevolence”, has been selected by high school students in a poll(民意调查)to highlight Chinese culture around the world. The character ren was selected by 8.33 percent of the 3. 000 respondents who took part in the poll, according to one of the organizers, a student from a high school.

It was followed by the characters ai, yi, meng and xiao, which mean ‘‘love”, “one”, “dream’’ and “filial piety”. Those characters ranked in the “top-20 most beautiful Chinese characters”.

China Dally, March 6, 2013. Page 4

你的短文应包括以下内容:

1. 简要概括学生推荐这五个汉字的理由。

2. 简述你最想推荐的一至两个汉字及其寓意。

3. 谈谈你的感想。

注意:

1. 对所有要点逐一陈述, 适当发挥, 不要简单翻译。

2. 词数150左右。开头已经写好, 不计入总词数。

3. 作文中不得提及有关考生个人身份的任何信息, 如校名、人名等。

Recently, some high school students conducted a poll asking people to choose some Chinese characters that Can best reflect Chinese culture.

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