题干

如图所示,某玻璃砖的截面由半圆和正三角形组成,半圆的直径为d,正三角形的边长也为d,一束单色光从AB边的中点D垂直于BC射入玻璃砖中,结果折射光线刚好通过半圆的圆心O,光在真空中的传播速度为c,求:

①光在玻璃砖中传播的时间(不考虑光的反射).

②人射光线的方向不变,将光在AB面上的入射点下移,使折射光线刚好能照射到圆的底部,入射点沿AB移动的距离为多少?这时光束在圆的底部经玻璃砖折射后的折射角为多少?

上一题 下一题 0.0难度 选择题 更新时间:2017-10-21 11:11:52

答案(点此获取答案解析)

解:①由几何关系可知,光在AB面上的入射角为60°,折射角为30°根据折射率公式有 n=sinisinr=sin

同类题4

完形填空

Lyle's Second Go

    In 1982,when I was coaching the Raiders, the owner of the team talked with me about a possible trade for Lyle Alzado. After watching him on tape,I didn't think he was that good, but the owner felt we could make Lyle better by creating the right environment lor him. We made the1.

    That summer at training camp,Lyle was having a hard time. He had that look in his eyes that many young players and some old players get when things aren't going 2.One morning Lyle came into my office and he looked like he hadn't slept. Here was a huge man, with his head about as3as it could go. We talked, or rather, I listened. The main point was that Lyle felt his career (职业生涯)was over and it would be best for him and for the team if he retired (退役).He apologized for4us since we had just traded for him.

    Lyle was always an emotional person. This is one of the reasons he was a good player. He5all that emotional energy with him, ready to lire out at the snap of the ball (开球).Now he was in front of me, almost crying. I thought for a moment, realizing we had to keep that 6going. Then I went through my reasons why he should not retire. At the end of our talk, I said,“You go out and play your very best, and let us7if you still have it. Personally, I think you do.”

    In January 1984. Tampa Bay Stadium. Super Bowl XVIII. With less than two minutes remaining, we were leading 38-9. We were the world champions of professional football. I saw Lyle,crying like a baby. I had to turn away quickly,or I would have joined him in 8.

    I remembered that morning in my office, and what Lyle, and what the Raiders, had achieved since he came to us. If Lyle hadn't given his career another shot, he wouldn't have had this victory. Maybe the Raiders wouldn't have had this victory. During that moment, I felt one of the greatest satisfactions of my coaching career.