matter and expose in X-ray film. This discovery led immediately to the use of

X-rays in medicine, a use we are familiar with.

3. Although Roentgen discovered the properties of X-rays he did not know

what the rays were. He therefore called them X-rays, the X standing for their

unknown nature. Today scientists know X-rays to be electromagnetic radiation of

extremely high frequency and therefore of extremely short wave length. X-rays

are considered to be produced whenever rapidly moving electrons bombard any

solid material. The greater the atomic weight of the material, the more plentiful

the X-rays, the greater the speed of the electrons the higher the frequency of

the X-rays.

4. As mentioned above X-rays were in a wide use for diagnostic purposes

in medicine since their discovery. Industrial radiology has been discovered

later particularly for inspecting welds and castings in the automobile and

airplane industries. Flaws and cracks inside the metal are readily revealed due

to the use of X-ray techniques. Famous paintings are often X-rayed to determine

whether they are the originals or forgeries.

5. Using X-rays- irradiation the scientists have learnt to change

structures of well-known materials such as metals, ceramics, etc. They could

obtain materials, of greater strength with higher melting point and particular

electrical properties.

6. Radiation is known to be a mutagenic agent. In microbiology mutations

are increased by irradiation. When a large-scale production of penicillin was introduced

the best strain yielded 100-200 units of penicillin. Being irradiated with

X-rays, the same strain produced more than 1.000 units. Many new uses have been

found for this treatment, in agriculture.

5. Прочтите 6-й абзац текста и вопрос к нему. Из

приведенных вариантов ответа укажите номер предложения, содержащего правильный

ответ на поставленный вопрос.

Ответы:

The increase obtained in the productivity of penicillin being irradiated

with X-rays was 800 to 900 units.

5. Прочтите 6-й абзац текста и вопрос к нему. Из приведенных вариантов ответа укажите номер предложения, содержащего правильный ответ на поставленный вопрос.

What increase was obtained in the productivity of penicillin being irradiated

with X-rays?  — Being irradiated withX-rays, the same strain produced more than 1.000 units.