Double

Doubly refracting crystals, such as calcite and quartz, break up light rays into two parts, called ordinary rays and extraordinary rays, which are polarized at right angles to each other. Such a crystal has a different refractive index for each of the two rays, and they are bent at different angles when they enter the crystal. This double refraction will form two images when a calcite crystal is placed over a dot on a piece of paper. The dot appears as two dots a small distance apart. Rotating the crystal causes one of the dots to rotate about the other. The dot that remains stationary is the image formed by the ordinary ray. This always lies in the plane of incidence (plane including the normal and the incident ray). The moving dot is the image formed by the extraordinary ray. [pg. 55] [Light and Color, by Clarence Rainwater, Prof. of Physics, San Francisco State College, Original Project Editor Herbert S. Zim, Golden Press, NY, Western Publishing Company, Inc., 1971.]

The purest , most universal form of motion is the spiral: the counterclockwise spiral, the levogyre, is the one found most often in nature. We discover it in the growth of trees and in other members of the vegetable kingdom, in the majestic sweep of the great spiral galaxies, in the long bones of animals, and in seashells. There are also many instances of double spirals--the two intersecting curves in the seed heads of ripe sunflowers, in the centers of daisies., the seed cones of fir trees. Like curves, spirals are not all the same. [Harlan, Calvin. Vision & Invention, An Introduction to Art Fundamentals. Englewood Cliffs, NJ: Prentice-Hall, 1986.]

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1 Double adj [ME, fr. OF, fr. L d upus [akin to Gk diploos], fr. duo two + -plus multiplied by; akin to OE -feald -fold -more at Two-Fold] [13c] 1: having a twofold relation or character: Dual 2: consisting of two usu. combined members or parts [an egg with a __ yolk] 3a: being twice as great or as many [__ the number of expected applicants] b of a coin: worth two of the specified amount [a __eagle] [a __ crown] 4: marked by duplicity: Deceitful 5: folded in two 6: of extra size, strength, or value [a __ matini] 7: having more than the normal number of floral leaves often at the expense of the sporophylls 8 of rhyme: involving correspondence of two syllables [as in exciting and inviting] 9: designed for the use of two persons [a _- room] [a __ bed]

2 Double vt [13c] 1: to make twice as great or as many: as a: to increase by adding an equal amount b: to amount to twice the number of c: to make a call in bridge that increases the value of odd tricks or undertricks at [an opponent's bid] 2a: to make of two thicknesses: Fold b: Clench [doubled his fist] c: to cause to stoop 3: to avoid by doubling: Elude 4a: to replace in a dramatic role b: to play [dramatic roles] by doubling 5a: [1]: to advance or score [a base runner] by a double [2]: to bring about the scoring of [a run] by a double b: to put out [a base runner] in completing a double play -vi 1a: to become twice as much or as many b: to double a bid [as in bridge] 2a: to turn sharply and suddenly; esp: to turn back on one's course b: to follow a circuitous course 3: to become bent or folded usu. in the middle -usu. used with up [she doubled up in pain] 4a: to serve an additional purpose or perform an additional duty b: to play a dramatic role as a double 5: to make a double in baseball

3 Double adv [14c] 1: to twice the extent or amount 2: two together

4 Double n [14c] 1: something twice the usual size, strength, speed, quantity, or value: as a: a double amount b: a base hit that enables the batter to reach second base 2: one that is the counterpart of another: Duplicate as a: a living person that closely resembles another living person b: Wrath c [1]: Understudy [2]: one who resembles an actor and takes his or her place esp. in scenes calling for special skills [3]: an actor who plays more than one role in a production 3a: a sharp turn [as in running] : Reversal b: an evasive shift 4: something consisting of two paired members; as a: Fold b: a combined bet placed on two different contests c: two consecutive strikes in bowling 5pl: a game between two pairs of players 6: an act of doubling in a card gaeme 7: a room [as in a hotel] for two quests -compare single4

Doubly adv [15c] 1: in a twofold manner 2: to twice the degree