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【单选题】关于沿着z轴放置的，中心在原点O的总长度为2h的对称振子，沿z轴放置且中心在原点，下列说法错误的是( )。
A.
h ≤ λ 时，最大辐射方向为θ =π/2。
B.
h ≤ λ/2 时，零功率波瓣宽度为 180度。
C.
h≤λ/2 时，半功率波瓣宽度随长度增加而变窄。
D.
h ≤ λ 时，振子臂上的电流是同向的。
【单选题】Now, our biggest summertime question has been answered: Why do people look so much better in sunglasses Vanessa Brown, a senior lecturer of art and design at Nottingham Trent University, gave an insid...
A.
demonstrate how to make better use of sunglasses
B.
explain why sunglasses improve appearance
C.
describe the evolution of sunglasses
D.
introduce the major functions of sunglasses