The above figure shows the motion of a progressive wave along a string. The particle motion of the medium is in direction

The above figure shows the motion of a progressive wave along a string. The particle motion of the medium is in direction

Answer Details

The particle motion of the medium in a progressive wave is perpendicular to the direction of wave propagation. In the given figure, the wave is propagating along the x-axis (OX), so the particle motion of the medium is in the direction perpendicular to OX, which is the y-axis (OY). Therefore, the answer is "parallel to OY".