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(gè)雷達(dá)兵的小弟弟問(wèn)他:“吉姆,能告訴我雷達(dá)的工作原理嗎?”
“雷達(dá)發(fā)射器發(fā)射出短促的電磁波脈沖,被目標(biāo)反射,由一個(gè)特殊的接收器接受。因?yàn)殡姶挪ǖ膫鞑ニ俣瓤梢詼?zhǔn)確地知道,而且它們傳播到目標(biāo)的時(shí)間以及返回的時(shí)間都可以在很大程度上準(zhǔn)確地知道,因此,可以探測(cè)出目標(biāo)的距離以及目標(biāo)的方向。”
他的小弟弟思考了一會(huì)兒,說(shuō)道:“既然你不知道,吉姆,為什么你不直說(shuō)呢?”