$$y = 0.02\left( m \right)\sin \left[ {2\pi \left( {{t \over {0.04\left( s \right)}}} \right) - {x \over {0.50\left( m \right)}}} \right]$$

But $$y = a\sin \left( {\omega t - kx} \right)$$

$$\therefore$$ $$\omega = {{2\pi } \over {0.04}} \Rightarrow v = {1 \over {0.04}} = 25\,Hz$$

$$k = {{2\pi } \over {0.50}} \Rightarrow \lambda = 0.5m$$

$$\therefore$$ velocity, $$v = v\lambda = 25 \times 0.5\,m/s = 12.5\,m/s$$

Velocity on a string is given by

$$v = \sqrt {{T \over \mu }} $$

$$\therefore$$ $$T = {v^2} \times \mu = {\left( {12.5} \right)^2} \times 0.04 = 6.25\,N$$