Abstract : This thesis presents the results obtained from two atom-optic experiments. The first part of this thesis is devoted to the study of the roughness of an atomic mirror. The light shift in an evanescent wave at the surface of a prism is used to reflect atoms falling from a magneto-optical trap. We present a method using interferometry to measure the evolution of the atomic coherence upon reflection on the mirror. The second part of the manuscript deals with an atom chip experiment. The magnetic field created by microfabricated wires, which constitute the chip, allows us to trap and manipulate cold atoms. We have obtained a Bose-Einstein condensate in the trap created by the chip. This trap shows significant roughness which we measure and explain the origin. Finally, we investigate the realization of integrated atom-optic elements, such as an interferometer, on an atom chip.