题干

图中关于光学现象的描述或解释不正确的是(   )

A:小孔成的是倒立的虚像

B:凹透镜可以矫正近视眼

C:白光通过三棱镜会分解成多种色光

D:漫反射的光线遵循光的反射定律

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答案(点此获取答案解析)

A

同类题2

阅读

                                                                                                      ____________

     一天中午,烈日炙烤着大地,知了不时鸣叫:“热死了,热死了……”

    吃午饭时,我向妈妈提了个问题:“妈,有这样一个成语:‘逆水行舟,不进则退’,是什么意思?”妈妈想了想说:“娜娜,现在不解释,下午带你去游泳吧。”我一听去游泳,特别高兴,一下子就把一碗饭吃得精光。

    下午,妈妈带我去东门河,路上,我又提起了那个问题。妈妈说:“游泳时你会明白。”

    到了河边,我换上游泳衣就钻进水里。一会儿仰泳,一会儿蛙泳,有时还来个鲤鱼跳龙门,妈妈不时地夸奖我,我快活极了。

    突然,妈妈好像想起了什么,不再欣赏我的精彩表演,对我说:“向上游。”我听清了妈妈的话:“向上游?哼,有什么了不起,游就游。”

    于是,我奋力向上游,一个大浪过来。我来不及躲避,被呛得鼻子发酸,耳朵里也灌了水,竟顺流而下,我只好游到浅滩。过了一会儿,我又迎着急浪向上游,但感到越来越吃力,双脚像灌满了铅。我使出吃奶的力气,只前进了几次,稍一松劲,就被急浪冲到岸边……

    妈妈见此情景对我说:“你体会到成语‘逆水行舟,不进则退’的意思了吗?”“什么?”我丈二和尚摸不着头脑。“你刚才向上游,稍不努力,不仅不能前进,反而后退。这个成语的意思是说:向水流相反方向行船,不努力前进就会后退。它也告诉人们,在人生道路上,不迎难而上,时代的潮流就会抛弃你。”

    哦,听妈妈这么一说,我仿佛懂得了许多……

同类题5

阅读理解

When settlers (移民)came to America during the 1600s, they were surprised to find so many trees. Some trees were so huge that a large man could not put his arms around them. Those trees helped the settlers a lot. They were glad and thankful to have these trees. They used them to build houses and make fire. From the wood of the trees, they made furniture, tools and so on.

Most people thought the forests would last forever. However, by 1800, America had its first wood shortage (短缺). How did it happen? People had not known that trees were being cut down faster than new ones could grow.

Some American people made trips to foreign countries. There they saw destroyed forests and learnt the importance of protecting forests. They came back to the United States and warned that if Americans didn’t use trees more carefully and wisely, someday the forests would all be gone. However, people were not ready to listen. Years went by, and America’s forests kept disappearing. It made some people really worried. But they did nothing.

Finally, J. Sterling Morton, the man who is remembered as the father of Arbor Day (过节), got people to listen. He named a Tree-Planting Day, or Arbor Day. He worked hard to make Arbor Day a national holiday. On that day, people usually plant a lot of trees.

Today, millions of trees have been planted in the United States because of Arbor Day. Arbor Day is such a good idea that many other countries now also have Arbor Day. Many, many trees are being planted all over the world because of J. Sterling Morton’s work.