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TEXT 7 A

ALBERT EINSTEIN

(1879-1955)

“Imagination is more important than knowledge”

Einstein

Albert Einstein was born in Germany on March 14,1879.His unusual ability to mathematics and physics began to show itself at a technical school in Zurich. At the age of 21 after four years of university study, Albert Einstein got a job as a clerk at an office. But already in 1905 he made revolutionary discoveries in science. He published three papers. In the first he explained the photoelectric effect by means of Planck’s quantum theory. The second paper developed a mathematical theory of Brownian motion. He presented his third paper on “Special Theory of Relativity” to a physical journal. Einstein expressed his theory in the equation E=mc², roughly that energy equals mass times the square of the speed of light.

All over the world scientists read the work with great surprise. Few physicists understood its importance at that time. Everybody wanted to know where he taught and in what laboratory he did his research.

Albert Einstein was a very talented man, a great thinker. He had an ability to look at the world with eyes full of wonder. All problems were new to him and he liked to solve them in his own way.

Einstein’s fame among scientists grew slowly but surely. For a few years he lived in Prague where he worked as a professor. When he came to Prague, he often told his students he would always try to help them. ”If you have a problem, come to me with it, we’ll solve it together”, he said.

He liked questions and answered them at once, for there were no simple or foolish questions for him. He spoke much with his students about scientific problems and his new ideas. His advice to young students was, “Don’t take easy problems”.

Einstein continued his research. His unified field theory was the result of 35 years of intense work. He expressed it in four equations where he combined the physical laws that control forces of light and energy with the mysterious force of gravitation.

In 1922 Einstein got the Nobel Prize in physics not for the theory of relativity but for a logical explanation of the photoelectric effect.

He gave all his life to the increase of human knowledge. His ideas produced revolution in the natural science of the 20th century.

TEXT 7 B

IT IS INTERESTING TO KNOW…

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…that Alfred Nobel, a Swedish chemist and engineer, was known for the invention of dynamite. Everything that he invented served military purposes. He understood how terrible his inventions were, but he easily forgot about them saying: ”The things which we develop are terrible indeed, but they are so interesting and so perfect technically that it makes them more attractive.”

But one morning, while looking through a French newspaper Nobel read about…his own death. The paper described his inventions as “terrible means of destruction” and he was named “a dynamite king” and “a merchant of death”.The thought that his name would always be connected with dynamite and death shook Nobel. He felt he could never be happy again. He decided to use all his money (about 2,000,000 pounds) for some noble purpose.

According to his will, prizes for “the most outstanding achievements” in physics,chemistry,medicine,literature and fight for peace are awarded every year. Nobel prizes have become the highest international scientific awards. Perhaps it’s an irony of life that some of Nobel prize winners helped to make the atom bomb.

TEXT 7 C

EINSTEIN’S PHOTOELECTRIC LAW

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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.

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