试题分析:依题意,波可沿+x或-x方向传播,故A错.而12m="(n+"
)λ,(n=0、1、2……).0.5s ="(m+"
)T,(m=0,1,2……)即波长可为:24m,8m, 4.8m……周期可为1s
s,
s, …,则波速可为: 4.8 m/s,8 m/s,24 m/s,14.4 m/s,72 m/s,40 m/s, 120m/s……选项C错误;选项BD正确;故选BD
点评:本题难度较小,属于波的多解问题,错解:认为(a,b相距必为半个波长,0.5s必是半个周期,即λ=24m,T=1s,故v= 24m/s