如图所示，M是一块平面镜，位于透明液体之中，镜面水平向上放置，一细束光线a竖直向下射来，穿过液体射到平面镜上，现将平面镜绕水平轴在竖直面内顺时针转动
角，光线经平面镜反射后在液面处分成两束，这两束光线恰好垂直，求；
（1）求该液体的折射率。
（2）若使光线经平面镜反射后在液面处恰好发生全反射，平面镜由初始水平位置绕水平轴在竖直面内顺时针转过的最小角度（用三角函数表示）。
（1）n=
（2）sin2θ=/3
| 基础知识 从所给单词中选用单词的适当形式填空。 | |
2. She was given a medal as a _______ for her service. 3. The paper should be ___________ in half. 4. The general said all means will be used to end the ___________. 5. It is ___________ to drive through a red light. . 6. I ___________ a great deal of work in the last few months. 7. They scouted around for some antiques to ___________ their new apartment. 8. She agreed to employ me for a ___________ period. 9. I will show ___________ for my friends even if it is only a comforting word. 10. Experts say many current___ plans do not have enough money to provide the benefits promised to workers. 11. She finally ___________ from her room at noon after staying there for the whole morning. 12. He can't ___________ himself to the whirl of modern life in this big city. 13. The company had no choice but ___________ $10 million for advertising. 14. The hunter hurled his___________ at the tiger. 15. The magazine was packaged in a___________ plastic case with attractive graphics. |