光指示器经常与幻灯片放映机一起使用.A light pointer is often useful with a slide projector.对于这种情况, 外框或角上的调节大小指示器更实用.For that situation, frame or corner resizers are better idioms.面板上的指示器将出现闪光,对操作者发出出现这种情况的警告.The operator is alerted to thi...
以太,能媒一种在以前被假定为电磁波的传播媒质并具有''.'绝对'.''连续性 、 ''.'高度'. ''弹性的极其稀薄的媒体.An all - pervading , infinitely elastic, massless medium formerly postulated as the medium of pro...