© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. Propagation of an electromagnetic pulse in a monolayer surface with a hot point is studied. Refractive index in the monolayer is changed locally. It is assumed that the perturbation to the dielectric function in each point (x,y) is described by a term proportional to 1/r, where r is the distance from the hot point to (x,y). An electromagnetic pulse is sent along the monolayer and its propagation is studied by solving the Maxwell equations numerically in the dielectric surface. This is the ondulatory version of the optical geometric approach presented by Selmke and Cichos in a didactic manner [Am. J. Phys2013, 81 (6), 405–413.]. Once the pulse passes through the hot point, a small perturbation appears in the front wave (photothermal signal). The numerical solution is found in several points and additional information is obtained by making the Fourier Transform of the signals.