Text 7b
IT IS INTERESTING TO KNOW...
Give a summary of the text.
After inventing dynamite, Swedish-born Alfred Nobel became a very rich man. However, he foresaw its universally destructive powers too late. Nobel preferred not to be remembered as the inventor of dynamite, so in 1895, just two weeks before his death, he created a fund to be used for awarding prizes to people who had made worthwhile contributions to mankind. Originally there were five awards: literature, physics, chemistry, medicine, and peace. Economics was added in 1968, just sixty-seven years after the first-awards ceremony.
Nobel's original legacy of nine million dollars was invested, and the interest on this sum is used for the awards which vary from $30,000 to $125,000.
Every year on December 10, the anniversary of Nobel's death, the awards (gold medals, illuminated diploma, and money) are presented to the winners. Sometimes politics plays an important role in the judges' decisions. Americans have won numerous science awards, but relatively few literature prizes.
No awards were presented from 1940 to 1942 at the beginning of World War II. Some people have won two prizes, but this is rare; others have shared their prizes.
Text 7c einstein's photoelectric law
Translate the text using a dictionary.
To explain the characteristics of thermal radiation, that is, the radiation emitted by hot bodies, Planck (1900) suggested that the emission and absorption of radiant energy by matter is in discrete quanta of energy h.
Einstein (1905) extended this hypothesis and postulated the quantum nature of radiation itself.
It is further seen that the absence of a time lag in photoelectric emission arises naturally, the absorption of quantum energy is instantaneous as is the resultant emission of an electron. This is to be contrasted with the hitherto accepted view that radiation consists of waves; the energy in the incident beam is spread uniformly over the area of the surface on which it falls. An electron which is at the surface or near it requires some time (of the order of seconds), to absorb sufficient energy from the beam to be able to escape from the surface.
The simplicity of Einstein's equation conceals the revolutionary nature of the concept underlying it. Light and all forms of radiation are emitted, and absorbed, in quanta of energy; the quanta are localized in space.
This is in fact a corpuscular theory, a beam of light or other radiation consisting of a stream of corpuscles called photons. Every photon moves with the velocity of light, and has a definite energy hv.
The study of the photoelectric effect was of major importance for the development of physical theory during the first two decades of the 20th century. The role played by the photoelectric effect during this period was largely due to the manner in which it displayed the quantum properties of radiation, which are not describable by the electromagnetic wave theory.
TEXT 7
QUANTUM ELECTRONICS
Quantum electronics was born when a new method was proposed for generating and amplifying radio waves by the use of quantum micro-systems, molecules, atoms and so on. This method has proved very fruitful and gave good results.
On the basis of radio-frequency quantum generators clocks have been made that measure time with an accuracy of one second per 300 years. Modern scientific achievements make possible the manufacture of clocks which measure time with an even higher accuracy, namely: one second per tens of thousands of years. Such super precise generators can be applied for aerial and sea navigation.
Of no less importance are the quantum amplifiers, they considerably increase the sensitivity of radio receivers. Quantum amplifiers operate at temperatures close to absolute zero, and radio receivers developed on the basis of quantum amplifiers are tens and even hundreds of times more sensitive than conventional receivers. This considerable increase in sensitivity opens up great future for radar, radio navigation, space radio communication, radio astronomy and other fields of science and technology.
Perhaps the most interesting thing about semiconductor lasers is that they can transform electrical energy directly into light wave energy. They do this with an efficiency approaching one hundred per cent. The development of powerful highly-efficient semiconductor lasers will considerably raise the power efficiency of a number of technological processes. Calculations and experiments show that even super hard substances such as diamonds, rubies, hard alloys and so on can be worked profitably by means of ruby lasers.
Semiconductor quantum generators occupy a special place among the optical quantum generators. The size of a ruby crystal laser comes to tens of centimeters. Ruby crystals about ten centimeters long can intensify light ten times. The same results can be obtained from semiconductor crystals only a few microns long.
Semiconductor laser is a few tenths of a millimeter long, whereas the density of its radiation is hundreds of thousands of times as great as that of the best ruby lasers. Semiconductor lasers operate under pulse and permanent regimes. It is very easy to control the generator oscillations, to modulate its radiation by simply changing its feed current. The high-frequency radiation of optical generators makes it possible to transmit an enormous flow of information. This is of great significance for the advancement of communication techniques. The small dimensions of the semiconductor laser make it especially suitable for use in super speed computers.
Theoretical calculations have shown that devices similar to semiconductor lasers can also transform the energy of light waves into electrical energy with an efficiency of close to 100 per cent. This means that electric power may be transmitted over considerable distances with negligible losses without the use of transmission lines. The high efficiency of semiconductor lasers opens up possibilities of developing extremely economical sources of light.