$v=\frac{v}{2 L}=480 \mathrm{\,Hz}$
For a pipe closed at one end, frequency of first harmonic,
${v^{\prime}=\frac{v}{4 L^{\prime}}=480 \mathrm{\,Hz}}$
$\therefore 4{{\rm{L}}^\prime } = 2{\rm{L}}$ or ${{\rm{L}}^\prime } = \frac{{2{\rm{L}}}}{4} = \frac{{\rm{L}}}{2}$
$y = \frac{{10}}{\pi }\,\sin \,\left( {\frac{{2\pi }}{T}t - \frac{{2\pi }}{\lambda }x} \right)$
For what value of the wavelength the wave velocity is twice the maximum particle velocity ..... $cm$ ?

If the distances are expressed in cms and time in seconds, then the wave velocity will be ...... $cm/sec$