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Polarized light is a probably phenomenon characterized by its ______.
A．rotational symmetry.
B．charged particles.
C．radiation flashes.
D．frequent twists.
答案
更多“Polarized light is a probably phenomenon characterized by its ______.A．rotational symmetry”相关的问题
第1题
But by far tile most startling and tentative finding is that the universe has a preferred orientation. Such directionality would challenge one of the basic tenets of physics and astronomy, taken for granted by Einstein, Newton and even Kepler. These giants all assumed that space possesses a property called rotational symmetry: spin a chunk of cosmos sideways or flip it upside down, and measurements of events within it yield precisely tile same results.
In the April 21, 1997 issue of physical Review Letters, however, Borge Nodland of the University of Rochestre and John P. Ealston of the University of Kausas present evidence that the principle of rotational symmetry may be violated on a cosmic scale. Measurements of light from distant galaxies, they say, vary depending on the galaxies' position in the sky.
Other theorists doubt whether the claim will stand up to close scrutiny; at least two critical analyses have already been posted on the Internet. For the moment, however, even the critics can savor the frisson of a tremor rocking their field' s foundations. "Nobody would be happier than me if they were right," says Sean M. Curroll of the University of California at Santa Barbara.
The surprising work on cosmic asymmetry began three years ago, while Nodland was working for his doctorate under Ralston's supervision. Ina search for signs of unconventional large - scale non - uniformity, the two researchers decided to investigate whether polarized light front remote galaxies changes with their direction or distance. (Polarized light typically swings within one plane rather than in all directions, ordinary sunlight does; it can be produced by a variety of phenomena. ) Polarized light often twists as it penetrates through space as a result of its encounters with electromagnetic fields; this well- understood phenomenon is called the Faraday effect. But Nodland and Raison wondered whether additional twisting effects might be at work.
To find out, they focused on studies of galaxies that emit large amounts of synchrotron radiation, a highly polarized form. of electromagnetism generated by charged particles passing through a strong electromagnetic field. After combing through the published literature, Nodland and Ralston compiled polarization data for 160 galaxies.
Their investigation involved a crucial assumption, that the initial angle of polarization of the light relative to the plane of each galaxy was the same for all 160 galaxies. Given this assumption and the estimated distances to the galaxies (inferred from their red shifts), Nodland and Ralslon could calculate whether the light underwent any twisting other than that caused by the Faraday effect.
The departure of the splendid Hale-Bopp comet is mentioned______.
A．to honor the contributions of Hale-Bopp.
B．to introduce to the topic of new report on cosmic matters.
C．to challenge the basic tenets of astronomy.
D．to recount the reactions of the public to the comet.
第2题
Birds deserve credit not merely for demonstrating flight was possible, but for providing templates for the shape of aircraft wings. The wings of birds suggested the pattern for leadingedge wing slots that improve ascent at slow speeds and for conical cambered wingtips that increase lift and stability. Other characteristics of bird wings, such as a trailing edge flap to aid in smooth landings, were not recognized as important until they had been designed independently by aeronautical engineers. Considerable research effort in aeronautics could probably have been saved by more thorough analysis of bird flight.
The insect world has also contributed significant ideas in the realms of navigation and guidance. In order to aid airline navigation during take-offs and landings under adverse weather conditions, engineers developed a system for locating the sun when it was hidden by clouds through observing polarized light—light which travels in a single direction. The research was instigated(鼓励,激发)after studies of honey bees demonstrated that they used this mechanism to determine their location when the sky was darkened. In another credit to the insect world, the evasive guidance systems of certain missiles use angular acceleration detectors modeled after the multi-lensed eyes of houseflies which amplify subtle movements by splitting images into a mosaic(马赛克)resembling a large display of televisions tuned to the same channel.
Even entities which never take flight themselves are responsible for guiding the hand of aeronautical engineers. The winged seed of a palm tree was the model for an early glider, and the single-winged, autorotating maple seed was the prototype for a means of air-dropping cargo by parachute.
The author argues that money for aeronautical research money could be invested more efficiently if______.
A．more advanced products were used in airplanes
B．more research was devoted to studying bird flight
C．greater efforts were directed towards shape designs of aircraft wings
D．greater emphasis was put on guidance systems
第3题
A．Because the GDP per capita in France is substantially higher than in America.
B．Because France witnessed a sharp increase of inequality in income distribution.
C．Because income distribution is more polarized in America than in France.
D．Because the two countries adopted different methods of national-account measurement.
第7题
In the process, the light energy converts to heat energy.
A．reduces
B．changes
C．leaves
D．drops
第8题
Kate likes ______ clothes.
A．the light red or white
B．the light red or green
C．tile light red or purple
