Recently it has become possible to alter the velocity of gaseous atoms with radiation pressure from laser beams. In one experiment an atomic beam of sodium atoms was brought almost to a standstill by shinning lasers from six directions turned to the D-line of Na. In this “optical molasses” the atoms move sluggishly about with an average of 40. cm s-1 . Find the de Broglie wavelength of these atoms. (Using this method, a so-called Bose Einstein condensate has been made, an ultracold cluster of atoms that behaves like one giant atom.)​