Solve this:
Q.2. The displacement y of a wave travelling in by x-direction is given by $y={10}^{-3}\sin \left(800t-2x+\frac{\mathrm{\pi }}{3}\right)$ where x is expressed in meters and t in seconds. The speed of the wave motion (in m$s^{-1}$) is
(a) 400
(b) 800
(c) 1200
(d) 200