A light-amount adjusting apparatus includes two aperture diaphragms that move in such a direction that the two aperture diaphragms come close or get away with respect to an optical axis of an incident light to adjust a size of an aperture opening. This waveguide cavity is used to conduct Cavity Ringdown Absorption Spectroscopy of loss mechanisms in the cavity including absorption or scattering by gases, liquid, solids, andor optical elements. A method can comprise obtaining a plurality of keywords for content of a media presentation, associating a first keyword with a first tag cloud and associating a second keyword with a second tag cloud, and generating a program component for providing a dynamic tag cloud using the first and second tag clouds. A purchase price is determined for the multiplier based upon various factors including the expected value of the multiplier as applied to a lottery ticket.