【单选题】折射率为n2、厚度为e的透明介质薄膜的上方和下方的透明介质的折射率分别为n1和n3,已知n1<n2<n3.若用波长为l的单色平行光垂直入射到该薄膜上,则从薄膜上、下两表面反射的光束的光程差是
【判断题】《我的母亲》的作者老舍,原名舒庆春,字舍予。
【单选题】They had a good preparation (准备) for the project, so they had little ____ all the work. [ ]
C.
difficulty in finishing
D.
difficulties to finish
【简答题】如图所示单口网络,L1=4H, L2=2H,M=2H,则 该单口网络的等效电感是 ()H。
【单选题】What changes had Reilly's project brought about?
A.
much more free time to suf on the internet
B.
get higher productivity and better grades at school
【单选题】PowerPont 2010中新建文件的默认名是( )。