Diffraction of a scalar plane wave oblique incidence on a flat screen with a one thin slit

In the framework of this work, we discuss the problem of diffraction of a plane and time-harmonic field on a flat screen with a single narrow slit. As a rule, this problem is considered for the case of normal incidence. At the same time, for a number of applied problems, in particular, the absorption of solar radiation by photocells, it is interesting to consider the general case of oblique incidence. In this work, the problem is solved in the Fraunhofer approximation. An analytical dependence of the intensity of the diffracted field on the direction of observation, the slit length, and the wavelength of the incident radiation is obtained.