如图所示，一个半径为R的
透明球体放置在水平面上，一束蓝光从A点沿水平方向射入球体后经B点射出，最后射到水平面上的C点。已知OA＝
，该球体对蓝光的折射率为
。则：
（1）它从球面射出时的出射角β为多少？
（2）若换用一束红光同样从A点射向该球体，则它从球体射出后落到水平面上形成的光点在C的哪侧？
解：（1）设入射角为α，由几何关系可知：sinα＝
由n＝
可得：sinβ＝nsinα＝
所以：β＝60°
（2）由于红光的频率小于蓝光的频率，所以红光的折射率小于蓝光的折射率，因入射角相同，由n＝
可知红光的折射角小于蓝光的折射角，所以红光从球体射出后落到水平面上形成的光点在C的右侧
| The early expansion of the sugar industry was based on cane transported from two different parts of the Orient, first from India and second from the islands of the Southwest Pacific. From India, sugar cane was carried through the western regions of Asia into Arabia and later into the countries bordering on the Mediterranean. It was established in Sicily in about A. D. 703 and was carried to Spain in about A. D. 755. As early as A. D. 1,150, Spain had at least 75,000 acres of cane. During this early period sugar cane was grown largely to supply local wants. The Crusades were partly responsible for the further expansion and improvement of the sugar industry and for interesting Europeans in the use of sugar. |
One thing that caused the sugar industry to shift westward was ______.
A．the favorable climate in the Orient
B．better means of transportation
C．the Crusades
D．that cane came from different parts of the Orient