Angle of incidence i = angle between the incident ray and the normal. Angle of refraction r = angle between the refracted ray and the normal. Glass is denser than air, so when light passes from ...

Schematic of a grazing incidence small and wide angle X-ray scattering (GISAXS/GIWAXS) experimental setup showing the incident (αi) and the scattered angles along the horizontal (2θf) and vertical (αf ...

They are shaped in a way that refracts light so it focuses at a point. Just like ray diagrams showing reflection, all angles are measured from the normal – a line at 90° to the refracting surface.