The problem: Answer a question about this article:
Chopin arrived in Paris in late September 1831; he would never return to Poland, thus becoming one of many expatriates of the Polish Great Emigration. In France he used the French versions of his given names, and after receiving French citizenship in 1835, he travelled on a French passport. However, Chopin remained close to his fellow Poles in exile as friends and confidants and he never felt fully comfortable speaking French. Chopin's biographer Adam Zamoyski writes that he never considered himself to be French, despite his father's French origins, and always saw himself as a Pole.
What event was Frederic a part of when he arrived in Paris during the later part of September in 1831?
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The answer: the Polish Great Emigration

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In the last two decades, photovoltaics (PV), also known as solar PV, has evolved from a pure niche market of small scale applications towards becoming a mainstream electricity source. A solar cell is a device that converts light directly into electricity using the photoelectric effect. The first solar cell was constructed by Charles Fritts in the 1880s. In 1931 a German engineer, Dr Bruno Lange, developed a photo cell using silver selenide in place of copper oxide. Although the prototype selenium cells converted less than 1% of incident light into electricity, both Ernst Werner von Siemens and James Clerk Maxwell recognized the importance of this discovery. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the crystalline silicon solar cell in 1954. These early solar cells cost 286 USD/watt and reached efficiencies of 4.56%. By 2012 available efficiencies exceed 20% and the maximum efficiency of research photovoltaics is over 40%.
In the 1880s, who constructed the first solar cell?
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The answer: Charles Fritts

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Meanwhile, U.S. garrisons in Japan continually dispatched soldiers and materiel to reinforce defenders in the Pusan Perimeter. Tank battalions deployed to Korea directly from the U.S. mainland from the port of San Francisco to the port of Pusan, the largest Korean port. By late August, the Pusan Perimeter had some 500 medium tanks battle-ready. In early September 1950, ROK Army and UN Command forces outnumbered the KPA 180,000 to 100,000 soldiers. The UN forces, once prepared, counterattacked and broke out of the Pusan Perimeter.
Who had the fewest number of troops in Korea?
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The answer: KPA

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Equivalently, the smallness of the Planck constant reflects the fact that everyday objects and systems are made of a large number of particles. For example, green light with a wavelength of 555 nanometres (the approximate wavelength to which human eyes are most sensitive) has a frequency of 7014540000000000000♠️540 THz (7014540000000000000♠️5401012 Hz). Each photon has an energy E = hf = 6981358000000000000♠️3.581019 J. That is a very small amount of energy in terms of everyday experience, but everyday experience is not concerned with individual photons any more than with individual atoms or molecules. An amount of light compatible with everyday experience is the energy of one mole of photons; its energy can be computed by multiplying the photon energy by the Avogadro constant, NA 7023602200000000000♠️6.0221023 mol1. The result is that green light of wavelength 555 nm has an energy of 7005216000000000000♠️216 kJ/mol, a typical energy of everyday life.
What color of light is the human eye most sensitive to?
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The answer:
green