Length of the steel wire = 1.4 m.

Density of steel,

Mass per unit length of the wire, , where r is the radius of the wire.

Young’s modulus of steel,

Strain in the wire, .

Let the tension in the wire be F. Stress and strain are related by the modulus of elasticity as

So we have

Speed of wave propagation in a stressed wire is given by

Wavelength of the longest standing wave corresponds to the configuration when the two ends of the wire are nodes and there is only one loop. That is

Therefore, the lowest resonant frequency of the wire