如图所示,S1、S2为两个振动情况完全一样的波源,两列波的波长都为λ,它们在介质中产生干涉现象,S1、S2在空间共形成6个振动减弱的区域(图中虚线处),P是振动减弱区域中的一点,从图中可看出( )
A:P点到两波源的距离差等于1.5λ
B:P点始终不振动
C:P点此时刻振动最弱,过半个周期后,振动变为最强
D:当一列波的波峰传到P点时,另一列波的波谷也一定传到P点
My name is John. I am a pupil. I like to read books on Sundays. I live in a house beside the zoo. It's near the school. So I walk to school every day. Tom is my friend. He lives far from the school, so he goes to school by bus. He likes to play on the computer on Sundays.
下图是甘地在丹地海边俯身抓起一把食盐,这是他事业中最精彩的一个镜头。这个镜头出现的背景是( )
唐太宗、武则天、唐玄宗共同注意的问题是( )
如图所示为电磁铁和永磁体相互作用产生的磁场,请根据图中磁感线的方向标出永磁体A左端的磁极极性和电磁铁电源的“+”极.