Two sinusoidal waves of same amplitude of 1 cm  propagate in opposite directions along x-axis. Wavelength of each wave is 6 cm speed of each wave is 0.5 cm/s. Then at any time t, displacement of a particle from its equilibrium position is zero at

Frequency f=Vλ=0.56Hz=112HzWave number K=2πλ=2π6cm−1=π3cm−1Equation of wave-1, y1=1sinπx3−2π.112t and equation of wave-2, y2=1.sinπx3+2π.112.t∴ Equation of resultant wave is y=y1+y2=2.sinπx3.cosπt6cmFor the particles which are permanently at rest, y = 0∴ sinπx3=0⇒πx3=nπ n=1,2,3,.....⇒x=3n cm