10.Read and retell:

“How are new inventions made?”

“How are new inventions that change the face of the world made?” somebody asked Einstein. ”Quite simply,” answered Einstein. ”Everybody knows that something is impossible. Then quite by chance, there happens an ignorant man who does not know it and he makes the invention”.

Different means

During his visit to an observatory Einstein got interested in the gigantic telescope with a mirror of 2.5 meters in diameter.

“What do you need such a big instrument for?” asked Einstein’s wife.

“We use it to study the structure of the universe”, answered the director of the observatory.

“Really?” said the lady. ”My husband usually does it on the inside of an old envelope.”

TEXT 7 B

It is interesting to know… Give a summary of the text

…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

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 20^th 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.