Three similar wires of frequency n1, n2 and n3 are joined to make one wire. Its frequency will be
n=n1+n2+n3
1n=1n1+1n2+1n3
1n1=1n12+1n22+1n32
n=12lTm⇒n1l1=n2l2=n3l3=k
l1+l2+l3=l⇒kn1+kn2+kn3=kn
⇒1n=1n1+1n2+1n3+........