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Capacitor = A device used in electric circuitry to temporarily store electrical charge in the form of an electrostatic field. In lighting, a capacitor is used to smooth out alternating current from the power supply.
http://www.lrc.rpi.edu/programs/nlpip/lightingAnswers/mwmhl/...

Cosine Correction:As a beam of light is tilted so that it strikes a surface at an angle, the area covered by the beam increases. Since the amount of light in the beam remains constant, the illumination on the surface decreases. This decrease is proportional to the cosine of the angle, which the incident beam makes with a perpendicular to the surface.

The meter reading of a fully cosine-corrected light meter represents the true illumination of the light receiver regardless of the angle from which the light approches.

When the light detector at an angle, the reading on the light meter should equal the reading that would occur if the light meter were held perpendicular to the rays of light, multiplied by the cosine of the angle of incidence on the meter detector. Cosine correction is accomplished by using a specially designed white molded plastic diffuser receptor. The diffuser provides cosine correction to a high degree of refinements; thus the detector correctly evaluates the light intensity regardless of direction.
http://www.spectracine.com/sc-700.htm