  We discuss the propagation of electromagnetic (EM) waves in the
post-Newtonian approximation of the general theory of relativity. We consider
diffraction of EM waves in the static gravitational field of a massive
monopole. We develop a wave-theoretical description of the solar gravitational
lens (SGL) and show that with its enormous magnifying power of $\sim 10^{11}$
(for $\lambda=1~\mu$m) and angular resolution of $\lesssim 10^{-10}$ arcsec,
the SGL may be used for direct megapixel imaging of an exoplanet.
