It is common experience that our eyes do not perceive significant changes in\ncolor when we observe for long time an object continuously exposed to light.\nWe always see plants to be green in summer until in autumn factors external\nto our vision, such as changes in the length of daylight and temperature,\ncause the break-down of chlorophyll and, in turn, spectacular changes in\nplantâ??s colors. Likewise, the photocurrent produced in solar panels or field\neffect transistors achieves a steady state magnitude shortly after the start of\nthe illumination. The steady state photocurrent lasts until the illumination\nstops. Understanding the origin of the steady state response of a device or\nlight harvesting (LH) system to illumination with electromagnetic (EM)\nwaves motivates the research presented in this work. In our experiments, we\nused capacitors as LH systems and illuminated them with infrared (IR) light\nover an 80 hours time period. We investigated the interaction between light\nand matter by monitoring versus time the voltage output of the capacitors. By\ncombining modeling and experimental observations, we concluded that the\nsteady state voltage is established soon after the start of the illumination as\nthe consequence of the law of conservation of energy. We also found that the\nmagnitude of the voltage in the steady state depends on the power and period\nof the illuminating IR light, and on the capacitance of the capacitor. When\nlightâ??s power undergoes fluctuations, also the voltage produced by the capacitor\nand the surface charge density on the capacitors do so. These findings\nsuggest that the law of conservation of energy has a significant repercussion\nwhen light is absorbed by matter in the steady state, for example in the mechanism\nof vision in vertebrates. Likewise, these findings are true when light\nis emitted from matter, for example in the mechanism of formation of the\nCosmic Microwave Background (CMB).
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