IV. Match (21-30) with their definitions (A-L). There are two definitions that you do not need to use.

Supplementary Tasks :

For statements (21-30) chose the best alternative (A, B or C) to replace the expressions in italics:

1. Although conceived as distinct phenomena... (line 1)

A.differentB.sameC.similar

2.... while charged particles in motion produce and respond to magnetic forces as well. (line 4)

A.penetrate B. complete C.create

3.... as well as in many other areas of classical and contemporary physics. (line 12)

A.waysB.regionsC.fields

4....between a pair of charged particles works in the following manner ... (line 15)

A.behaviorB.roadC.method

5.... each particle responds to the force exerted upon it by the electric field ... (line 16)

A.depended B. influenced C.agreed

6.... by four remarkable equations formulated in the latter part of the 19th century ... (line 20)

A. wonderful B. unknown C. obscure

7.... as well as the manner in which changing magnetic fields produce electric fields... (line 24)

A.developingB.alteringC.returning

8.From these relations Maxwell inferred the existence of electromagnetic waves ... (line 26)

a. A.concludedB.thoughtC.decided

9.... detached from the charges that created them ... (line 27)

a. A.accompanied B. continued C. separated

10.... extends from long-wavelength radio waves to short-wavelength gamma rays ... (line 31)

a. A.continues B. follows C.stretches

IV. Determine the key message of the text. Choose the best alternative (A, B, C, D or E):

A. Electromagnetism studies electric and magnetic fields and their description.

B. The field concept is one of the main notions in the classical formulation of electromagnetism.

C. The laws of action of electric and magnetic fields are based on the principles of classical electromagnetism.

D. The nature of electric and magnetic fields depends on the motion of charged particles.

E. Many contributions have been made to the development of the theory of electromagnetism..

 

TEXT 4

RAYS AND RADIATION

(1)In 1864 Scottish scientist James Clark Maxwell made the brilliant deduction that light is a kind of wave created by the combined effects of electricity and magnetism. He also predicted that light might just be one of many kinds of “electromagnetic” radiation. Scientists were keen to find out, and in 1888 Heinrich Hertz built a circuit to send big sparks across a gap between two metal balls. If Maxwell were right, the sparks would send out waves of electromagnetic radiation. But they might not be visible like light. So Hertz set up another electric circuit to detect them. The waves created pulses of current in this circuit, which Hertz saw as tiny sparks across another gap. By moving the receiving circuit, he worked out just how long the waves were. They proved to be much longer than light waves, and are now known as radio waves. (2)About the same time others were experimenting with discharge tubes. Discharge tubes gave a near-perfect vacuum and the spark between the electrodes made the tube glow brightly. The glowing was named "cathode rays" because it seems to come from the negative terminal, or cathode. If the tube was empty, how was the spark crossing from one electrode to another? In 1897 J.J. Thomson guessed the spark was a stream of tiny bits of atoms, which he called electrons. For the first time, scientists saw that the atom is not just a solid ball, but contains smaller subatomic particles. (3)Meanwhile, in 1895 the discharge tube helped Wilhelm Roentgen to discover another kind of radiation. Roentgen found that, even when passed through thick card, some rays from the tube made a sheet of fluorescent material glow. Although card could block out light it could not stop these new mystery rays, which he called X-rays. (4)In the same year French scientist Henri Poincare wondered why the glass in discharge tubes often glowed as well as the sparks. Perhaps radiation might be emitted not only by electricity but by certain substances too. Soon Antoine Becquerel discovered this when he left uranium salts in a dark drawer on photographic paper. A few weeks later there was a perfect image of a copper cross that had been lying on the paper. There was no light or electricity to form the image, so where was the radiation coming from. (5)Marie and Pierre Curie soon found the intensity of radiation was in exact proportion to the amount of uranium. They realized it must be coming from the uranium atoms themselves, and called this atomic radiation "radioactivity". In fact, not only uranium, but also many other elements are radioactive, including two new elements discovered by the Curies – radium and polonium.