Grazing incidence refers to the physical phenomenon that occurs when light or other electromagnetic radiation strikes a surface at a very shallow angle relative to the surface plane. Because the angle of incidence approaches zero, the resulting interaction dramatically alters the measurable properties of the light, often leading to phenomena such as enhanced reflection or specialized diffraction effects. This characteristic is utilized in various fields of physical science and engineering, including characterizing material structures and measuring nanoscale dimensions. The physics governing grazing incidence requires consideration of the refractive index and the specific geometry of the interface, allowing for the study of material properties that would be obscured or fundamentally different at normal angles of illumination.