【简答题】双缝干涉实验中, 1 若双缝间距由 变为 ,使屏上原第十级明纹中心变为第五级明纹中心,则 : ;2若在其中一缝后加一透明媒质薄片,使原光线光程增加 ,则此时屏中心处为第 2 级 纹。
【单选题】Because of her peculiar characteristics, she has a lot of difficulty ______friends with her classmates.
【判断题】化妆品类的虚假广告较多是因为这些产品的功效很难被精确定量。()
【单选题】It costs her a lot of money, but she doesn't regret ________ a year traveling around the world.
【单选题】世界上第一台电子数字计算机ENIAC是( )年在美国问世的。
【简答题】双缝干涉实验中,若双缝间距由d1变为d2,使屏上原第10级明纹中心变为第5级明纹中心,则d2与d1的比值为
【判断题】加强工程建设项目合同管理,必须从企业法人做起,从项目经理做起和从工程师做起。
【单选题】Radio is used a lot because__________ _.A.it costs less than TVB.it costs more than
A.
30. Radio is used a lot because__________ _. A.it costs less than TV
C.
it is not so cheap as TV
D.
people can't know the news on TV