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【单选题】第二篇 Sleep We all know that the normal human daily cycle of activity is of some 7 - 8 hours’ sleep alternating with some 16 - 17 hours’ wakefulness and that, broadly speaking, the sleep n...
A.
people hate the inconvenience of working on night shifts.
B.
your life is disturbed by changing from day to night routines and back.
C.
not all industries work at the same hours.
D.
it is difficult to find a corps of good night workers.
【单选题】两个相干波源在同一空间传播，空间某点离两波源的波程差δ=r1-r2=( )，振幅最大。
A.
k×λ
B.
k×λ/2
C.
(2k+1)λ/2
D.
(2k+1)λ/4