A wave y = a sin (wt–kx) on a string meets with another wave producing a node at x = 0. The equation of the unknown wave is

On considering the wave equation,

y = – a sin (kx + wt)

On superposition the resulting wave equation is 

$\mathrm{y}=-2\mathrm{asinkxcos\omega t}$

At x=0, y=0 , wave produce node.