Unpolarized infrared emissivity of oil films on sea surfaces

The unpolarized infrared emissivity of oil films on sea surfaces is derived under the geometric optics approximation. The multiple reflections at each of interface are ignored, but the multiple reflections between the upper and lower interfaces of the oil film are taken into account. The oil film is assumed to be thin, so that the two interfaces can be considered as parallel and identical. Thus, under the geometric optics approximation, the oil film can locally be seen as a Fabry-Pe¿rot interferometer. Thus, the emissivity of the contaminated sea can easily be obtained from the emissivity of the air/oil interface only. Emissivity comparisons between clean and contaminated seas are then presented to study the oil film detectability.