Question

A mechanical wave propagates in a medium along the X-axis. The particles of the medium
(a) must move on the X-axis
(b) must move on the Y-axis
(c) may move on the X-axis
(d) may move on the Y-axis.

Answer 1

(c) may move on the X-axis
(d) may move on the Y-axis.

EXPLANATION:  

Mechanical waves are either transverse or longitudinal. In the transverse wave, the particles will move on Y-axis while in the longitudinal wave the particles will move on X-axis. So the particles of the medium may move on the X-axis or it may move on the Y-axis depending upon the nature of the wave.