deflection of the path of electrons (electron) as they pass through a solid (typically a metal, semiconductor, or insulator). Deflections, or collisions, are caused by electrostatic forces operating between the negatively charged electrons and atoms (atom) within the solid (see quantum electrodynamics). These forces reduce the speed of the electrons, thereby limiting the performance of electronic devices based on transistors (transistor) and integrated circuits (integrated circuit). The deflection of a beam of electrons by a target also is called electron scattering and has been used to probe the size and charge distribution of atomic nuclei. In the early 1970s, electron scattering helped to confirm that protons (proton) and neutrons (neutron) are made of still more elementary subatomic particles (subatomic particle) known as quarks (quark). See also cross section and electron diffraction.