QUES: In the last years of the nineteenth century, Planck was investigating the problem of black-body radiation first posed by Kirchhoff some forty years earlier. It is well known that hot objects glow, and that hotter objects glow brighter than cooler ones. The electromagnetic field obeys laws of motion similarly to a mass on a spring, and can come to thermal equilibrium with hot atoms. The hot object in equilibrium with light absorbs just as much light as it emits. If the object is black, meaning it absorbs all the light that hits it, then its thermal light emission is maximized.
What is known about the light absorption of a hot object in equilibrium with light?

ANS: absorbs just as much light as it emits

QUES: In Russia, the government began to actively encourage the proliferation of arts and sciences in the mid-18th century. This era produced the first Russian university, library, theatre, public museum, and independent press. Like other enlightened despots, Catherine the Great played a key role in fostering the arts, sciences, and education. She used her own interpretation of Enlightenment ideals, assisted by notable international experts such as Voltaire (by correspondence) and, in residence, world class scientists such as Leonhard Euler and Peter Simon Pallas. The national Enlightenment differed from its Western European counterpart in that it promoted further modernization of all aspects of Russian life and was concerned with attacking the institution of serfdom in Russia. The Russian enlightenment centered on the individual instead of societal enlightenment and encouraged the living of an enlightened life.
What century produced the first Russian univeristy, library, theatre, public museum, and independent press?

ANS: 18th century

QUES: The shelter of the early people changed dramatically from the paleolithic to the neolithic era. In the paleolithic, people did not normally live in permanent constructions. In the neolithic, mud brick houses started appearing that were coated with plaster. The growth of agriculture made permanent houses possible. Doorways were made on the roof, with ladders positioned both on the inside and outside of the houses. The roof was supported by beams from the inside. The rough ground was covered by platforms, mats, and skins on which residents slept. Stilt-houses settlements were common in the Alpine and Pianura Padana (Terramare) region. Remains have been found at the Ljubljana Marshes in Slovenia and at the Mondsee and Attersee lakes in Upper Austria, for example.
What type of homes were built in the Neolithic era?

ANS: mud brick houses

QUES: Color in glass may be obtained by addition of electrically charged ions (or color centers) that are homogeneously distributed, and by precipitation of finely dispersed particles (such as in photochromic glasses). Ordinary soda-lime glass appears colorless to the naked eye when it is thin, although iron(II) oxide (FeO) impurities of up to 0.1 wt% produce a green tint, which can be viewed in thick pieces or with the aid of scientific instruments. Further FeO and Cr2O3 additions may be used for the production of green bottles. Sulfur, together with carbon and iron salts, is used to form iron polysulfides and produce amber glass ranging from yellowish to almost black. A glass melt can also acquire an amber color from a reducing combustion atmosphere. Manganese dioxide can be added in small amounts to remove the green tint given by iron(II) oxide. When used in art glass or studio glass is colored using closely guarded recipes that involve specific combinations of metal oxides, melting temperatures and 'cook' times. Most colored glass used in the art market is manufactured in volume by vendors who serve this market although there are some glassmakers with the ability to make their own color from raw materials.
What can give glass a metal?

ANS:
unanswerable