半圆形玻璃砖的半径为R，直径MN，如图所示。一细束白光从Q点垂直于直径MN的方向

发布时间：2017-07-28 14:15 │ 来源：www.tikuol.com

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问题：

半圆形玻璃砖的半径为R，直径MN，如图所示。一细束白光从Q点垂直于直径MN的方向射入半圆形玻璃砖，从玻璃砖的圆弧面射出后，打到光屏P上，得到由红到紫的彩色光带。已知QM=R/2。如果保持入射光线和屏的位置不变，只使半圆形玻璃砖沿直径方向向上或向下移动，移动的距离小于R/2，则有

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A．半圆形玻璃砖向上移动的过程中，屏上红光最先消失

B．半圆形玻璃砖向上移动的过程中，屏上紫光最先消失

C．半圆形玻璃砖向下移动的过程中，屏上红光最先消失

D．半圆形玻璃砖向下移动的过程中，屏上紫光最先消失

考点：光的色散

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下列哪些因素会影响天线的水平空间分集增益？（）

A、天线高度

B、两天线间距

C、移动台与两天线连线中垂线的夹角

D、所用天线的数量

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Modern industrial society grants little status to old people. In fact, such a society has a system of built-in obsolescence. There is no formal system for continuing our education throughout our life in order to keep up with rapidly changing knowledge. When our education and job skills have grown obsolete, we are treated exactly like those who have never gained an education or job skills and are not encouraged or given the opportunity to begin anew.
As a society becomes more highly developed, the overall status of older people diminishes. Improved health technology creates a large pool of old people, who compete for jobs with the young. However, economic technology lowers the demand for workers and creates new jobs for which the skills of the aged are obsolete, forcing older people into retirement. At the same time, young people are being educated in the new technology and are keeping pace with rapid changes in knowledge. Finally, urbanization creates age-segregated neighborhoods. Because the old live on fixed incomes, they must often live in inferior housing. All these factors -- retirement, obsolete knowledge and skills, inferior standards of living -- lower the status of the aged in society.
A century ago, when one could expect to live only to 50 or so, the life span more or less coincided with the occupation and family cycle. But today the average life span allows for fifteen to twenty years of life after these cycles. It appears that our life span is outpacing our usefulness in society.

The sentence "our life span outpaces our usefulness" means we can live longer______.

A．and make progress

B．and do more work

C．but move slowly

D．but become useless

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程序运行时，向图片框P1中加载“C:\WINDOWS\Car. bmp”图像文件，应使用( )。

A．Picture1. Picture=("C:\WINDOWS\Car. bmp")

B．Picture1. Picture=LoadPicture("C:\WINDOWS\Car. bmp")

C．P1. Picture1=LoadPicmre(C:\WINDOWS\Car. bmp)

D．P1. Picture=LoadPicture("C:\WINDOWS\Car. bmp")

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中高层、高层住宅阳台栏杆净高不应低于( )m。

A．0.90
B．1.00
C．1.05
D．1.10

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子宫肌瘤合并妊娠时错误的叙述是

A．可发生红色变性

B．易发生浆膜下肌瘤蒂扭转

C．可引起阻塞性分娩

D．可引起产时宫缩乏力，产后出血

E．由于存在上述问题，故宜剖宫产结束分娩

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