问题 选择题

下列有关凸透镜的说法不正确的是

A.凸透镜对光有会聚作用

B.凸透镜可以矫正远视眼的视力

C.凸透镜所成的实像可以是放大的,也可以是缩小的

D.凸透镜所成的虚像可以是放大的,也可以是缩小的

答案

答案:D

题目分析:凸透镜对光有会聚作用,凸透镜可以矫正远视眼的视力,凸透镜所成的实像可以是放大的,也可以是缩小的,也可以是等大的,凸透镜所成的虚像只可以是放大的。

A.凸透镜对光有会聚作用 不合题意;

B.凸透镜可以矫正远视眼的视力 不合题意;

C.凸透镜所成的实像可以是放大的,也可以是缩小的 不合题意;

D.凸透镜所成的虚像可以是放大的,也可以是缩小的 符合题意;

故选D。

考点:本试题考查的是凸透镜成像。

点评:对于此类试题,学生应把握凸透镜的成像情况。

选择题
单项选择题

Come on, my fellow white folks, we have something to confess. Out with it, friends, the biggest secret known to whites since the invention of powdered rouge: welfare is a white program. The numbers go like this: 61% of the population receiving welfare, listed as "means-tested cash assistance" by the Census Bureau, is identified as white, while only 33% is identified as black. These numbers notwithstanding, the Republican version of "political correctness" has given us "welfare cheat" as a new term for African American since the early days of Ronald Reagan.

Our confession surely stands: white folks have been gobbling up the welfare budget while blaming someone else. But it’s worse than that. If we look at Social Security, which is another form of welfare, although it is often mistaken for an individual insurance program, then whites are the ones who are crowding the trough. We receive almost twice as much per capita, for an aggregate advantage to our race of $10 billion a year--much more than the $3. 9 billion advantage African American gain from their disproportionate share of welfare. One sad reason: whites live an average of six years longer than African Americans, meaning that young black workers help subsidize a huge and growing "over-class" of white retirees. I do not see our confession bringing much relief. There’s a reason for resentment, though it has more to do with class than with race. White people are poor too, and in numbers far exceeding any of our more generously pigmented social groups. And poverty as defined by the government is a vast underestimation of the economic terror that persists at incomes--such as $ 20,000 or even $ 40,000 and above--that we like to think of as middle class.

The problem is not that welfare is too generous to blacks but that social welfare in general is too stingy to all concerned. Naturally, whites in the swelling "near poor" category resent the notion of whole races supposedly frolicking at their expense. Whites, near poor and middle class, need help too--as do the many African Americans.

So we white folks have a choice. We can keep pretending that welfare is black program and a scheme for transferring our earnings to the pockets of shiftless, dark-skinned people. Or we can clear our throats, blush prettily and admit that we are hurting too--for cash assistance when we’re down and out, for health insurance, for college aid and all the rest. Racial scapegoating has its charms, I will admit: the surge of righteous anger, even the fun--for those inclined--of wearing sheets and burning crosses. But there are better, nobler sources of white pride, it seems to me. Remember this: only we can truly, deeply blush.

The expression "racial scapegoating" (Para. 4) best denotes()

A. anger at the mercy of laws

B. an aid in terms of prejudice

C. relief for the sake of classes

D. a victim in the name of races