题干

如图所示,一束单色光从空气入射到棱镜的AB面上,经AB和AC两个面折射后从AC面进入空气,当出射角i′和入射角i相等时,出射光线相对于入射光线偏转的角度为θ,已知棱镜顶角为α,则计算棱镜对该色光的折射率表达式为(   )

A:sinα+θ2sinα2

B:sinα+θ2sinθ2

C:sinθsin(θα2)

D:sinαsin(αθ2)

上一题 下一题 0.0难度 选择题 更新时间:2018-06-30 12:38:02

答案(点此获取答案解析)

A

同类题1

阅读理解

    One afternoon last week, I saw three tearful children from my son's school being comforted by teachers. That morning, my 11-year-old had stomach pains, retching(干呕)into a bowl. Talking to other mothers later, I heard about other children with stomachache or difficulty sleeping the night before.

What caused so much pain? Sports day. Sports day might be necessary at a highly-competitive independent school, but not at a village primary school. For the children who can fly like the wind, sports day causes no problem. For those who are overweight or just not good at sport, it is a nightmare(噩梦). Even for those who enjoy running but fall halfway down the track in front of the entire school and their parents, it can prove a disaster.

    Why do we put our children through this annual suffering? Some may say competition is character building; or it's taking part, not winning, that's important; or that it is a tradition of school life. I just felt great pity for those children in tears or in pain.

    Team games at the end of sports day produced some close races, wild enthusiasm, lots of shouting—and were fun to watch. More importantly, the children who were not so fast or quick at passing the ball were hidden a little from everyone's eyes. Some of them also had the thrill of being on the winning side.

    I wish that sports day could be abandoned and replaced with some other less-competitive event. Perhaps an afternoon of team games, with a few races for those who want them, would be less stressful for the children and a lot more fun to watch.