The article describes a methodology for studying Fresnel diffraction with the active involvement of students in discussing the results of a demonstration experiment. To create a clearly visible model of Fresnel zones, a centimeter radio wave range was chosen, in which the first zone is about 10 cm in size. This makes visible the created combinations of open and closed sections of the wavefront and allows students to predict the results of demonstrations. To maintain the cognitive activity of students, the method of creating and resolving educational contradictions, problem situations is used.