So, $\lambda=\frac{4 L}{5}=8 \mathrm{\,cm}$
$A_{s}=(2\, m m) \sin (k x)=(2\, m m) \sin \left(\frac{2 \pi}{\lambda} x\right)$
${=(2 \mathrm{\,mm}) \sin \left(\frac{2 \pi}{8 \mathrm{cm}} \times 1 \mathrm{cm}\right)} $
${=(2 \mathrm{\,mm}) \sin \left(\frac{\pi}{4}\right)=\sqrt{2} \mathrm{\,mm}}$
${z_1},{z_2}$ and ${z_3}$ as${z_1} = A\sin (kx - \omega \,t)$, ${z_2} = A\sin (kx + \omega \,t)$ and ${z_3} = A\sin (ky - \omega \,t)$.
Which of the following represents a standing wave

