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
1n2 = 1n21+1n22+1n23
n = 12lTm ⇒ n1l1 = n2l2 = n3l3 = k
l1+l2+l3 = l ⇒ kn1+kn2+kn3 = kn
⇒1n =1n1+1n2+1n3+....