The little brother of an Army radar operator asked,“Jim,tell me how does a radar work?”
“The radar transmitter emits brief impulses of electromagnetic waves which are reflected from the target and received by a special receiver.Since the speed at which electromagnetic waves propagate is exactly known and the time they take to travel to the target and back can be determined with a great degree of accuracy,it is possible to determine the range to the target as well as the direction to it.”
His brother pondered a moment,then said,“As long as you don’t know,Jim,why don’t you just say so?”
一個雷達兵的小弟弟問他:“吉姆,能告訴我雷達的工作原理嗎?”
“雷達發(fā)射器發(fā)射出短促的電磁波脈沖,被目標反射,由一個特殊的接收器接受。因為電磁波的傳播速度可以準確地知道,而且它們傳播到目標的時間以及返回的時間都可以在很大程度上準確地知道,因此,可以探測出目標的距離以及目標的方向?!?
他的小弟弟思考了一會兒,說道:“既然你不知道,吉姆,為什么你不直說呢?”