Light has always intrigued humans. Whether it was the light from the sun or the light from a fire, we have used light and made light when none was naturally available. The interaction of light with different materials has long been studied. Research by scientists in the late nineteenth century led to an intriguing discovery. Light, under the right conditions, creates a small voltage (ejects electrons) when shined on certain metals. Einstein eventually explained this photoelectric effect, adding to our essential understanding of the nature of light. This discovery formed the foundation for a technology which later became known as photovoltaic cells. Photovoltaic cells are the materials found in the solar panels shown in the figure above. The solar panels shown here can generate enough electricity throughout the day to power 5 average American homes (assuming an average monthly energy use of about ~1000 kWh). Photovoltaic cells have become quite affordable and are now a reasonable alternative for electricity generation.
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