波长为λ的单色平行光垂直入射到薄膜上,已知n12>n3,如图所示。则从薄膜上、下两表面反射的光束①与②的光程差是:()
A.
B.
C.
D.
参考答案:B
If you _____ this now,you _____ to college. [ ]
A. don't do;will never go
B. won't do;won't do
C. don't do;never will go
D. do;will go never
明朝后期的进步思想家是( )。
A.李贽
B.王夫之
C.黄宗羲
D.顾炎武