**3.1 Theoretical module**

The basis of diffraction is explained. Fresnel and Fraunhofer diffraction is explained using some typical apertures. For instance, Fig. 1(b) shows diffraction patterns for a single slit, multiple slits, and circular aperture, which in turn produces the well-known Airy disc. The user can navigate back and forth through a multi-page environment using the ✄ ✂ ✁ Next and ✄ ✂ ✁ Previous buttons. ✄ ✂ ✁ APPLICATION button brings the user to the Simulation module described in section 3.2. The ✄ ✂ MANUAL button launches the users's manual of the tool. ✁

(b) Theoretical explanation of diffraction

Fig. 1. Diffraction tool: main screen and example of the theoretical module
