The loss of light as it passes through a material, generally due to its conversion to other energy forms (typically heat)

(anti-reflective) A coating layer with a thickness exactly equal to one quarter of the optical wavelength. The light which is reflected directly on this surface will negatively interfere with the portion of light that is reflected from the boundary face between the thin coating and the glass substrate. For AR-coatings, metal and dielectric materials can be selected.