In the rigorous electromagnetic simulation of an imaging system, the evanescent waves from a point source or from a sample are naturally mixed with the propagative waves. Therefore, their contributions are difficult to distinguish. We present a point-source model made of only the evanescent waves. To illustrate its potential, the model is applied to the study of the evanescent-wave contribution in microsphere-assisted microscopy (MAM). The contribution of the evanescent waves in the microsphere imaging process is clearly demonstrated. However, we also show that this contribution is not enough to justify the super-resolution. The destructive interference between two close point sources may be the key physical phenomenon.