单项选择题
A.λ B.2λ C.3λ D.4λ
A.5nλ B.5λ C.2.0nλ D.2.5nλ
A.8cm B.16cm C.30cm D.0
A.(1/2)π B.π C.2π D.无法确定
A.y=Acosω[t-(x-L)/u] B.y=Acosω[t-(x+L)/u] C.y=Acosω[t+(x+L)/u] D.y=Acosω[t+(x-L)/u]
A.1/3 B.1/4 C.2/5 D.2/7
A.0.973 B.0.027 C.0.954 D.0.982
A.1 B.2 C.3 D.4
A.(-1,1) B.(-1,1) C.(3,7) D.(4,5)