题干

如图,一个三棱镜的截面为等腰直角ABC,为直角。此截面所在平面内的光线沿平行于BC边的方向射到AB边,进入棱镜后直接射到AC边上,并刚好能发生全反射。该棱镜材料的折射率为  (    )

A:

B:  

C:

D:

上一题 下一题 0.0难度 选择题 更新时间:2019-06-09 06:37:18

答案(点此获取答案解析)

A

同类题2

阅读下面短文,掌握其大意,然后从各题所给的A,B,C,D四个选项中选出最佳选项。

    A thousand years ago, Hong Kong was covered by a thick forest. As more and more people came to 1 in Hong Kong, these trees were cut down and burnt. Now there is 2 forest left, though there are still some small areas covered with trees. We call these woods, not forests.

    Elephants,tigers and many 3 animals were living in the thick forest. When people came to live in Hong Kong, the 4 began to die out. Early farmers grew rice and kept pigs and chickens in the valleys (山谷). They cut down the trees and burnt them. They needed fire to keep themselves 5 in winter, to cook their food and to keep away the dangerous animals. Elephants 6 disappeared because there was not enough food for them. So did most of the wolves and tigers. Monkeys and many other animals soon died 7 the same way.

    You might think that there are no longer any animals in Hong Kong except in the zoos. There  8 still about 36 different animals living there. One of the most interesting of Hong Kong's animals is the barking deer (麂). These are beautiful little animals with a rich brown coat and a white patch(补丁) under the tail. They look like deer but they are much smaller. They are less than two feet  9 . They make a noise rather like a dog barking. In Hong Kong the barking deer has only one real enemy – 10 . People hunt these little animals though it is illegal (违法的). There are now not many barking deer left. So it is important for people to protect wild animals.

同类题3

阅读下面的文字,完成小题。

惩罚微笑

黄飞

    一位内地企业家到香港办厂,他住的别墅到停车地要经过一段“S”形草地,其实路很短。那天,他出门晚了,一急便从草地上直接穿过,跨过低栏就上车。这时,一位年轻的香港警察走了过来,很礼貌地给他撕了张罚单,处罚280元港币。他愣了,根本没想到这会是事。280元港币折合人民币也不过区区300元,问题是太丢面子了,而且丢在香港。这对于一个处处让人仰视、处处有人伺候、什么事都不用自己操心、什么事都可以摆平的领导来说,心理上无论如何难以接受。但,现在没人帮他。这是在香港,就他们两个人。一个西装革履的内地大老总,面对一个一脸稚气的香港警察。他哀叹,只有靠自己了。

    那时,阳光极好,从维多利亚港湾升起的朝阳,温柔异常,将老总的面孔照得红扑扑的。他尴尬地笑着,赶忙递上盒好烟,低三下四地说:“对不起,我错了。主要是有急事……”那年轻警察也笑了。他虽然听不懂老总那半土半洋的普通话,但明白意思,摆摆手很礼貌地谢绝了香烟。老总见对方笑了,且很真诚,松了口气,脸上的笑容更灿烂了,使劲比划着:“我保证,下不为例,绝对下不为例!”年轻警察始终微笑着。老总的心彻底放下了。他收起罚单,向对方亲切地拜拜一声,开车走了,在警察微笑的目光中渐渐远去。

    这件事,很快忘记了。一星期后,他收到了法院的传票。老总莫名其妙,没做犯法的事啊!急忙找律师,律师问他近日有无犯规的情况。他苦思冥想,猛地想到了那次过草地,可已经解决了呀!律师听后摇头道:“你误会了,绝不可能那样解决。按香港法律,一个星期不到指定地点交罚款,法院传你;再不理睬,就要拘捕你。”老总慌神了,忙请律师疏通。律师认真说道:“这不比内地,没用的,我也不会去疏通。最好的办法,老老实实认错受罚。”老总没辙了。

    开庭那天,还有几个犯规的人。老总确实老实,见到法官,就点头哈腰地笑。法官问他犯规事实,他一一承认,毫不犯犟。谁知审判结果,其他人都按罚单罚,惟独他加罚一倍:560元港币。他憋气,又不敢问,交了罚款就去找律师。律师也莫名其妙,建议他直接去问法官,并说这是法律允许的,很正常。老总想了想,鼓起勇气,决定学秋菊讨个说法,罚要罚个明白,不能当冤大头。去一问,法官很严肃:“你违反了法规,自己也承认,可你一见法官就笑,这本身就是藐视法庭,所以加重处罚。”

    老总简直傻了!后来,他忍不住将这个“教训”逢人便讲……

    这是个真实的故事。在一次会议上,一位从香港归来的代表说的。当时听的人哈哈笑过之后又陷入了深思。

    我在想,一向威严的老总,为什么要逢人就讲这个“教训”呢?原因只有一个:刺激太大了。在内地标准的皮毛小事,在香港却如此较真;循规蹈矩地去处理,却连栽跟头;“不打笑面人”的古训,在这里受到了无情的嘲弄;传统的思维模式,在这块同属于中国的土地上碰得头破血流。