LuftGlasGrenzflächen

LuftGlasGrenzflächen refers to the boundary between air and glass in optical systems. At such interfaces light moves between media with different refractive indices, typically air with about n ≈ 1.00 and glass with n ≈ 1.45–1.60, depending on the glass type.

When light meets an air–glass boundary, part of the light is reflected and part is transmitted. This behavior follows Snell's law, n1 sin θ1 = n2 sin θ2, where n1 and n2 are the refractive indices of air and glass respectively. At normal incidence, the reflectance is R = ((n2 − n1)/(n2 + n1))^2; for air–glass with n2 ≈ 1.5, R ≈ 4%, so about 96% of the light is transmitted.

Angle-dependent effects also arise. The Fresnel equations describe how reflectance varies with polarization and incidence angle. There is a Brewster angle for air-to-glass, θB ≈ arctan(n2/n1) ≈ 56°, at which p-polarized light experiences minimal reflection. From glass to air, total internal reflection can occur above a critical angle θc = arcsin(n2/n1). For a typical glass (n ≈ 1.5), θc is about 41.8 degrees.

Applications and mitigation: LuftGlasGrenzflächen are central to lenses, windows, and fiber optics. Reflections reduce transmission and can cause glare. Anti-reflective coatings employ thin-film interference to cancel reflections over specified wavelengths, while surface finishing and index-matching fluids help control reflections and improve transmitted light.