  A theory of evanescent mode atomic mirrors utilising a metallic sheet on a
dielectric substrate is described. The emphasis here is on the role of the
metallic sheet and on the evaluation of atomic trajectories using the field-
dipole orientation picture. At low intensity, the atomic reflection process is
controlled by two separate mechanisms both of which are modified by the
presence of the metallic sheet and influenced by the use of the field-dipole
orientation picture. The first mechanism involves the spontaneous force which
accelerates the atom parallel to the sheet plane. The second mechanism involves
the combined dipole plus van der Waals force which acts to repel the atom from
the surface, decelerating its motion until it attains an instantaneous halt
before changing direction away from the surface at an appr opriate turning
point in the trajectory. Various quantitative features arising from varying the
controllable parameters of the system, including screening effects as well as
desirable enhancement effects, are pointed out and discussed.
