c
(c) Maximum particle velocity \({v_{\max }} = \omega a\) and wave velocity \(v = \frac{\omega }{k}\)

==> \(\frac{{{v_{\max }}}}{v} = \frac{{\omega a}}{{\omega /k}} = ka\).

From the given equation \(k = {\rm{Co - efficient}}\;{\rm{of}}\,x = 6\,micron\)

\(\; = 6 \times {10^{ - 6}}m\)

==> \(\frac{{{v_{\max }}}}{v} = ka = 6 \times {10^{ - 6}} \times 60 = 3.6 \times {10^{ - 4}}\)