1. Incandescent lamp — лампа накаливания

2. "Cold" daylight lamp — «холодная» лздша дневного света

TRANSMITTING PICTURES BY TELEPHONE

Pictures can now be sent over the telephone by sound signals. A new machine does this by looking at a picture and telling what it sees over the telephone to a similar machine at the receiving end, which then translates the sound signals it hears back into the form of a picture.

At the sending end, the photograph, drawing business form or document is placed in the machine. At the receiving end, the reproduction appears on ordinary paper. An illus­tration of ordinary letter size takes six minutes to be re­ceived and reproduced.

This is how the machine works.

Inside the machine optical devices rotate and pick tip reflected light which is focused on and passed through a filter to a photocell or "electronic eye". The photocell generates a signal which is amplified to produce voltages uf varying strength.

The voltages are converted into sound, and it is this audible signal which is transmitted over the telephone, just as music or voice is transmitted.

At the receiving telephone, the sound is reconverted to an electronic signal and then into a varying voltage. This voltage is applied to a drive mechanism. The mechanism is activated to extend and print out a corresponding dark area of the transmitting picture. The length of the document determines the time needed for transmission.

THE ATOM STRUCTURE

Our atomic age is more than 2000 years old. More than 2000 years ago Greek philosophers discussed the structure of the atom. One of the philosophers, Democritus, suggested that all matter consisted of particles which are invisible and indivisible, the Greeks called this particle the atom.

The idea of atomic structure of matter was later almost forgotten and came to life again ¹ at the beginning of the 19th century when the English scientist, John Dalton, introduced into science the idea of the elements, the basic building particles of matter.

Then, after many years of careful research, the discovery of the electron, a part of an atom, was announced.

The discovery of the electron was only the first step in the exploration of the inner world of the atom. Since it was known that the atom was electrical ly.neutral the phys­icists now began to search for the positive particles which could balance out the negative charge of the electron.

In 1911 another English scientist, Ernest Rutherford, discovered that the atom had a core, or nucleus, in its centre, and that the nucleus was positively charged and contained nearly all the weight of the atom. He showed that the positive charge of the nucleus was caused by particles called "protons".

In 1932 the third basic atomic particle, neutron, was discovered. The weights of the parts of the atom were cal­culated very carefully and it was found that the proton and neutron have almost the same weight, but that they are much greater in mass than the electron.

The atom as we think of it today is mostly empty space. In the centre there is a tiny core, or nucleus, containing neutrons and protons. Electrons orbit around the nucleus at a distance which is really very small, but is large for the tiny world of an atom. Other particles have been also found inside the atom, but protons, neutrons and electrons are the main bricks of atomic structure.

Note