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问题 计算题

（10分）如图所示是一种折射率的棱镜。现有一束光线沿MN方向射到棱镜的AB面上，入射角的大小i＝60°，求：

（1）光在棱镜中传播的速率；

（2）画出此束光线进入棱镜后又射出棱镜的光路图，要求写出简要的分析过程。

答案

（1）   （2）

（1）光在棱镜中传播的速率   （2分）

（2分）

（2）由折射率得：AB面上的折射角。

由几何关系得：BC面上的入射角

全反射临界角

则光在BC面上发生全反射，光线垂直AC射出。（2分）

光路如图所示（4分）

本题考查光的折射定律，和公式v=c/n的应用，由光路图和全反射条件可判断光线在BC面发生全反射

单项选择题

计算涨价预备费的公式PC＝∑It[(1+f)t-1]中，f代表( )。

A．资金时间价值
B．建设期价格上涨指数
C．银行贷款利率
D．财务基准收益率
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单项选择题

Throughout the 19th century and into the 20th, citizens of the United States maintained a bias against big cities. Most lived on farms and in small towns and believed cities to be centres of (1) , crime, poverty and moral (2) Their distrust was caused, (3) , by a national ideology that (4) farming the greatest occupation and rural living (5) to urban living. This attitude (6) even as the number of urban dwellers increased and cities became an essential (7) of the national landscape. Gradually, economic reality overcame ideology. Thousands (8) the precarious (不稳定的) life on the farm for more secure and better paying jobs in the city. But when these people (9) from the countryside, they carried their fears and suspicions with them. These new urbanities, already convinced that cities were (10) with great problems, eagerly (11) the progressive reforms that promised to bring order out of the (12) of the city.

One of many reforms came (13) the area of public utilities. Water and sewerage systems were usually operated by (14) governments, but the gas and electric networks were privately owned. Reformers feared that the privately owned utility companies would (15) exorbitant (过渡的) rates for these essential services and (16) them only to people who could afford them. Some city and state governments responded by (17) the utility companies, but a number of cities began to supply these services themselves. (18) of these reforms argued that public ownership and regulation would (19) widespread access to these utilities and guarantee a (20) price.

（7）（）

A.feature

B.peculiarity

C.quality

D.attribute
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