题干

下列关于凸透镜和凹透镜的说法正确的是(  )

A:凸透镜的焦距越小,其对光的会聚作用就越小

B:凹透镜的焦距越小,其对光的发散作用就越小

C:光无论沿什么方向射向凹透镜的光心后,其传播方向不发生改变

D:光无论沿什么方向射向凸透镜后,都能会聚在凸透镜另一侧的焦点上

上一题 下一题 0.0难度 选择题 更新时间:2018-06-28 07:09:00

答案(点此获取答案解析)

C

同类题2

A

                                                                                    The Boy Made It!         

         One Sunday, Nicholas, a teenager, went skiing at Sugarloaf Mountain in Maine. In the early afternoon, when he was planning to go home, a fierce snowstorm swept into the area. Unable to see far, he accidentally turned off the path. Before he knew it, Nicholas was lost, all alone! He didn’t have food, water, a phone, or other supplies. He was getting colder by the minute.
           Nicholas had no idea where he was. He tried not to panic. He thought about all the survival shows he had watched on TV.It was time to put the tips he had learned to use.
       He decided to stop skiing. There was a better chance of someone finding him if he stayed put. The first thing he did was to find shelter form the freezing wind and snow. If he didn’t, his body temperature would get very low, which could quickly kill him. Using his skis, Nicholas built a snow cave. He gathered a huge mass of snow and dug out a hole in the middle. Then he piled branches on
 top of himself, like a blanket, to stay as warm as he could.
           By that evening, Nicholas was really hungry. He ate snow and drank water from a nearby stream so that his body wouldn’t lose too much water. Not knowing how much longer he could last, Nicholas did the only thing he could- he huddled(蜷缩) in his cave and slept.
The next day, Nicholas went out to look for help, but he couldn’t find anyone. He followed his tracks and returned to the snow cave,because
 without shelter, he could die that night. On Tuesday, Nicholas went out to find help. He  had   walked for about a mile when a volunteer
 searcher found him. After two days stuck in the snow, Nicholas was saved.
           Nicholas mightnot have survived this snowstorm had it not been for TV. He had often watchedGrylls’ survival show. Man vs. Wild. That's where he learned the tips that saved his life, In each episode(一期节目)of Man vs. Wild, Grylls is abandoned in a wild area and has to find his way out.
          When Grylls heard about Nicholas’ amazing deeds, he was super impressed that Nicholas had made it since he knew better than anyone how hard Nicholas had to work to stay alive.