Photoemission intensities from core levels derived from surface and bulk atoms of a solid exhibit oscillations as a function of the excitation photon energy. These oscillations cannot be described by the classical layer attenuation model, which has been the basis for intensity analysis and quantitative structural modeling in a number of studies. The physics responsible for these oscillations is the extended photoemission fine structure (EPFS) above the core level absorption edge, which contains structural information in regard to surface bond lengths. The present paper examines in detail this phenomenon for the Si 2p core level of the Si (111)−(7×7) surface. The EPFS is found to modulate the surface-to-bulk Si 2p core level intensity ratios up to ~50%; thus, structural models based on a surface-to-bulk intensity ratio analysis using the classical layer attenuation model at a few photon energies may suffer large errors. This EPFS may be responsible for the ongoing debate in the literature over the assignment of the surface core levels to structural features on both the (111) and (100) surfaces of Si and Ge. This dilemma is resolved for the (7×7) surface. Using the usual three-component fit of the Si 2p core level (a bulk component and two surface components, S1 and S2), the EPFS signals from the individual components are separately analyzed. The results show the S2 component to be derived from adatom emission. The S1 component is unresolved, and represents emission from several different types of atoms in the top double layer of the (7×7) reconstruction.