With both ends of the cord fixed one obtains the lowest possible
resonance frequency (first
harmonic) when no further
nodes
appear in the oscillatory movements of the cord.
This frequency must be such that the space between the two ends of the cord,
 ,
corresponds to half of the wavelength,
=λ/2.
Since the speed of waves in the cord, v,
is supposed to be constant, one has
v = f × λ
→
f = v / 2
The places of zero displacement
are called nodes (nós ou nodos),
whereas the places of maximum displacement
are called anti-nodes (ventres).
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