+ \(u_M = A cos \frac{2 \pi x}{\lambda }.cos(\omega t)\)
+ \(A_M = A.\left | cos \frac{2 \pi x}{\lambda } \right |\)
\(\left\{\begin{matrix} x =3,5 cm\\ T = 0,02 s; v = 1,5 m/s \Rightarrow \lambda = v.T = 3 cm\end{matrix}\right.\)
\(\Rightarrow A_M = A. \left | cos \frac{2 \pi.3,5}{3} \right | = 0,5 A\)