Context and question: A CD is read by focusing a 780 nm wavelength (near infrared) semiconductor laser housed within the CD player, through the bottom of the polycarbonate layer. The change in height between pits and lands results in a difference in the way the light is reflected. By measuring the intensity change with a photodiode, the data can be read from the disc. In order to accommodate the spiral pattern of data, the semiconductor laser is placed on a swing arm within the disc tray of any CD player. This swing arm allows the laser to read information from the centre to the edge of a disc, without having to interrupt the spinning of the disc itself.
What createds the change in light reflected off of a CD?
Answer: change in height between pits and lands
Context and question: The political reforms of Peter the Great ( , Pyotr Velikiy) were accompanied by a reform of the alphabet, and achieved their goal of secularization and Westernization. Blocks of specialized vocabulary were adopted from the languages of Western Europe. By 1800, a significant portion of the gentry spoke French daily, and German sometimes. Many Russian novels of the 19th century, e.g. Leo Tolstoy's ( ) War and Peace, contain entire paragraphs and even pages in French with no translation given, with an assumption that educated readers would not need one.
Who wrote 'War and Peace'?
Answer: Leo Tolstoy
Context and question: The development of writing enabled knowledge to be stored and communicated across generations with much greater fidelity. Combined with the development of agriculture, which allowed for a surplus of food, it became possible for early civilizations to develop, because more time and effort could be devoted to tasks (other than food production) than hunter-gatherers or early subsistence farmers had available. This surplus allowed a community to support individuals who did things other than work towards bare survival. These other tasks included systematic studies of nature, study of written information gathered and recorded by others, and often of adding to that body of information.
Having a surplus of food allowed farmers and hunter-gatherers to spend less time working on what?
Answer:
food production