for, . for + () + to : , , , . , , , , , , .
It required some minutes more for the pilot to know the
height of the flight.
,
.
:
It was important for us to use this new method.
.
| 1. , : to say, to state, to believe, to consider . 2. , : to hear, to feel, to watch, to notice . 3. , : to order, to ask, to request . 4. , : to seem, to appear, to happen, to prove . 5. : be likely, be unlikely, be certain . | He is said to live in Canada. We were seen to enter the theatre. The secretary was ordered to bring all documents. She seemed not to listen to him. They are likely to come soon. | , . , . , . , . , , . |
Complex Subject :
) .
(is said, is known, is believed .), 3- (, , .). , , .
Billions of stars are assumed to exist in the universe
2 1 3 4
,
) ( , , ), , .
The results are known to have been used in this experiment.
, , .
, (Complex Subject) . , .
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These forms of radiant energy have been found to travel through space with a big speed.
, , .
. to be .
Atoms were assumed to be indivisible particles of the elementary substance.
, () .
- - to be + likely to be + unlikely. Indefinite Infinitive .
Under these conditions the output is likely to increase.
.
(to have been) .
This scientist is supposed to have developed a new method.
, .
, .
This method does not seem to offer any advantages.
, .
, .
Such reaction was not observed to happen.
He , .
ENERGY AND ELECTRONS
The structure of the atom is similar to planetary system, electrons orbiting around a central nucleus. Electrons also rotate about their own axes. We know the rate of electron rotation and the orbital path determine the amount of energy possessed by the atom.
The total energy contained in any atom is known to be the sum of the energies of the individual electrons. Electrons of a given atom can be changed from their position by different energies. Radioactive materials, for example, are constantly undergoing a change. Radioactive energy emitted from the material changes it from one form to another. It is also possible to change the atom structure by means of controlled nuclear reaction. The atomic bomb and the hydrogen bomb are known to be example of great amount of energy contained in an atomic structure. There are much simpler methods of changing the amount of energy in a given atomic structure. Aphotoelectric cell, for example, has a large area photocathode made from chemically active materials. These materials are known to be alkali metals.
They are electrically active to the degree that they emit electrons when struck by light.
Light falling on the cathode will cause electrons to be emitted; the anode being supplied with a positive potential, electrons will be attracted toward it, producing a photoelectric current. This is well-known photoemissive cell; it has many uses in modern industry. Basic laws governing the photoelectric effect were studied by Stoletov. They are also true for the laser operation. There are two basic laws of photoelectricity.
The first law is known to state that the number of electrons released per unit of time from photoelectric surface is directly proportional to the intensity of the incident light. Thus, the more intense light, the greater is the number of electrons to be released. This law states that the greater the light intensity, the greater is the current flow in the photoelectric cell.
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The second law is known to state that the maximum energy of electrons coming from photoelectric surface is independent of the intensity of the incident light and is directly proportional to the frequency of the light. It can be shown experimentally that the maximum energy of electrons depends only on the frequency of the light falling of the cathode surface. The higher the frequency of incident of radiation, the higher is the energy of photoelectrons.
The photoelectrons the light energy which falls on the photocathode excites the outers of the atoms. Thus, the light energy causes photoemission.
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Vocabulary notes
nucleus (pl. nuclei) ()
to undergo -,
hydrogen bomb-
photoelectric cell-
photocathode -
alcali metals-
photoemissive cell- ,
incident light-
to excite -
GRAMMAR EXERCISES
I. Find in the text the sentences with the Subjective Infinitive construction and translate them.
II. Say if it is true or false.
1. Electrons are orbiting around a central nucleus.
2. The total energy contained in any atom is known to be sum of the energies of the individual nuclei.
3. There are two basic laws of photoelectricity.
4. Light falling on the anode will cause electrons to be emitted.
