Michael Whelan conducted pioneering work to develop the transmission electron microscopy technique for the study of defects in crystals. He was responsible both for establishing many of the basic experimental techniques, and for the theories of image contrast essential for the detailed interpretation of the micrographs. His treatment of image contrast from a stacking fault based on the dynamical theory of electron diffraction forms the basis of all subsequent work on image contrast from defects. Together with Archie Howie, he was responsible for developing the theory of image contrast from dislocations, and he has also made important contributions to the understanding of absorption and inelastic scattering of electrons in crystals. He pioneered the development of a combined electron microscope and energy analyser for carrying out microanalysis on a very fine scale. His electron microscope study of dislocation reactions in face-centred cubic metals established and extended an important aspect of dislocation theory. He also developed the first direct method for measuring stacking fault energy (from the curvature of dislocations at nodes).
For their contributions to the theory of electron diffraction and microscopy, and its application to the study of lattice defects in crystals.