Problem: Glass has the ability to refract, reflect, and transmit light following geometrical optics, without scattering it. It is used in the manufacture of lenses and windows. Common glass has a refraction index around 1.5. This may be modified by adding low-density materials such as boron, which lowers the index of refraction (see crown glass), or increased (to as much as 1.8) with high-density materials such as (classically) lead oxide (see flint glass and lead glass), or in modern uses, less toxic oxides of zirconium, titanium, or barium. These high-index glasses (inaccurately known as "crystal" when used in glass vessels) cause more chromatic dispersion of light, and are prized for their diamond-like optical properties.
What is the refraction index of typical glass?
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Answer: 1.5


Problem: As of 2000[update], there were 59,948 people who were single and never married in the municipality. There were 49,873 married individuals, 9,345 widows or widowers and 9,468 individuals who are divorced.
How many people were married in Bern in 2000?
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Answer: 49,873


Problem: The Russian SFSR was controlled by the Communist Party of the Soviet Union, until the abortive 1991 August coup, which prompted President Yeltsin to suspend the recently created Communist Party of the Russian Soviet Federative Socialist Republic.
What event prompted the start of the control of the Communist Party of the Soviet Union in the RSFSR?
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Answer:
unanswerable