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w关键词：X-ray/X光，Rontgen/伦琴，ray/光线 |
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w目录：Science/科技 |
w话题：科技，发明 |
w类型：记叙文 |
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w难度级别：
初级 |
w词汇要求：800 |
w文章词数：650 |
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[ 生 词 可 拖 选 或 双 击 ] |
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X-rays were first
discovered by a German scientist
in
1895, almost by accident. |
The
discoverer of X-rays
Ｘ光的发现者
|
作者：Unknown |
来源：www.englishfree.com.cn |
|
日期：2008-4-6 |
责编：Emma |
(Wilhelm Konrad Rontgen, 1845-1923)
If you break your arm or leg, the
doctor will probably send you to hospital to have an X-ray
photograph taken to find out just where the break is and what
kind of break it is. If a small child swallows a coin or some
other hard thing, as sometimes happens, the doctor will take an
X-ray photograph to find out just where the object has got to in
the child's body.
Every hospital has an X-ray
department, and doctors now depend on these photographs for
giving them information about their patients. Dentists also take
X-ray photographs of people's teeth to find out if there is
anything wrong with the teeth which do not show from the
outside.
X-rays were first discovered by a
German scientist, Wilhelm Konrad Rontgen, in 1895, almost by
accident. He and several other scientists were experimenting
with passing electric currents through certain gases in a
special glass tube from which the air had been removed.
Then one day Rontgen noticed
that, even when the tube was covered with black paper, some
strange kind of radiation was coming through and making a screen
nearby glow. Rontgen could not see anything coming out of the
tube, but then he discovered that if he put the screen in the
next room on the other side of a closed door, the rays still
seemed to affect it. The glowing screen showed that the rays
could not only pass through black paper but also wood.
The next thing he found out was
that if he put his hand between the rays and a photographic
plate, the rays would print a shadow of the bony framework of
his hand on the plate. In fact, the rays could pass as easily
through the fleshy part of his hand as through the black paper,
but hardly at all through the bone. So Rontgen made the first
X-ray picture of a hand showing just how the bones in the hand
fit together.
When Rontgen wrote an account of
what he had discovered, he called these new rays X-rays, for X
is a symbol often used for something which is not yet
understood. Other scientists called them Rontgen rays in honor
of the man who first found them, but X-ray is the name now
always used.
Rontgen went on to try to find
out more about these strange invisible rays. It appeared that
they travel in a straight line, as light rays travel; but that
they are not bent, as light is, when passing through glass or
water. He gradually came to realize that X-rays, like light
waves, are electromagnetic radiations, but that their
wave-lengths are extremely short. This is why they can pass
through materials solid enough to stop ordinary light, and why
they are invisible to our eyes.
We now know that X-ray waves are
2,000 to 10,000 times shorter than light waves, and that the
shorter they are the more easily they will pass through solid
materials. Scientists have now discovered rays with even shorter
wave-lengths, which they call gamma rays, and which can pass
through even more solid substances than X-rays can.
As well as being used for taking
photographs, X-rays are also used for treating diseased parts of
the body to kill the disease. So today doctors can find out by
X-rays whether a patient has tuberculosis, for example, or
cancer, in time to be able to cure it, and then use the X-rays
to destroy the cancer. This is why people are encouraged to have
X-rays taken in the mass radiography units which go to schools
and factories and such places.
X-rays are also used for studying
many other things as well as human bodies. Engineers use them,
for example, to find out how metals are made up, to check
whether they will be strong enough for their purpose and whether
there are any flaws in them.
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