A self-sustained atmospheric pressure system for absorbing or scattering electromagnetic waves using a capillary discharge electrode configuration plasma panel and a method for using the same. Of particular interest is the application of this system to vary the level of exposure or duration of an object to electromagnetic waves, or as a diffraction grating to separate multiple wavelength electromagnetic waves into its respective wavelength components. The generation of the non-thermal plasma is controlled by varying the supply of power to the plasma panel. When a substantially uniform plasma is generated the plasma panel absorbs substantially all of the incident electromagnetic waves thereby substantially prohibiting exposure of the object (disposed downstream of the plasma panel) to the electromagnetic waves. If the generated plasma is non-uniform the plasma panel reflects at least some of the electromagnetic waves incident on its surface. When a multiple wavelength electromagnetic source is employed, the plasma panel scatters the waves reflected from its surface in different directions according to their respective individual wavelengths. The degree of separation between the various wavelength components depends on arrangement of and spacing between the capillaries. Thus, the system may be used as a diffraction grating for separating multiple wavelength electromagnetic waves into its respective wavelength components.