A wire is fixed at both ends has consecutive standing wave nodes for which the distance between the adjacent nodes are 18cm and 16cm respectively.The minimum possible length of the string is

A)128cm B)72cm C)64cm D)144cm

144 Ans.The question tells you distance between two adjacent nodes. This means it tells you the distance between the two nodes which are vibrating consecutive harmonious. So find a general term for distance between nth harmonic and n+1th harmonic in terms of length of string and wavelength. Make two equations and get the answer.