A,B是簡(jiǎn)諧波波線上距離小于波長(zhǎng)的兩點(diǎn)。已知,B點(diǎn)振動(dòng)的相位比A點(diǎn)落后π/3,波長(zhǎng)為=3m,則A,B兩點(diǎn)相距L =()m