$${\begin{array}{l} \lambda_x= \frac {2L} {n_x}= \frac {h} {mv_x}, n_x =1,2,3 ... \\ \lambda_y= \frac {2L} {n_y}= \frac {h} {mv_y}, n_y =1,2,3 ...\\ \lambda_z= \frac {2L} {n_z}= \frac {h} {mv_z}, n_z =1,2,3 ... \end{array} }$$