在图中画出点光源S发出的两条光线经凸透镜折射后的径迹.
图示的是一凸透镜,平行于主光轴的光线经凸透镜折射后折射光线通过焦点,过光心的光线其传播方向不变;如下图所示:
(2014·北京四中3月模考)It is well known that knowledge is________treasure house,but practice is________key to it.
A.a;the
B.the;the
C.a;/
D./;the
“数量及单位”栏:( )。
A.50463kg,100000m
B.50200kg,100000m
C.10000m
D.50463kg