The present study investigates electromagnetic diffraction by a pulse from 2-D dielectric objects. A narrow Gaussian beam in the time domain is employed as the incident electromagnetic waves with a large period. The reflected field from the scatterer differs from the object's dimension, orientation, and relative permittivity. Therefore, the object's location, orientation, and electrical and physical properties can be deduced from the difference in the reflected field characteristics in the time domain. The Method of Auxiliary Sources (MAS) is employed to obtain the results.