X-ray : X-Ray
X-rays (German: Röntgenstrahlen) are a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm - 10 nanometers (corresponding to frequencies in the range 30 PHz - 60 EHz).
X-rays with a wavelength longer than 0.1 nm are called soft X-rays. At wavelengths shorter than this, they are called hard X-rays. Hard X-rays overlap the range of long-wavlength (low energy) gamma rays, however the distinction between the two terms refers to the source of the radiation, not its wavelength: X-ray photons are generated by energetic electron processes, gamma rays by transitions within atomic nuclei.
History
X-rays were first observed and documented in 1895 by Wilhelm Conrad Röntgen, a German scientist who found them quite by accident when experimenting with vacuum tubes. Later, he took an X-ray photograph of his wife's hand which clearly revealed her wedding ring and her bones. On January 12, 1896 H.L. Smith[?] was the first person to take a x-ray photograph and the X-ray machine was exhibited for the first time on January 18. The photograph electrified the general public and aroused great scientific interest in the new form of radiation. Röntgen called it "X" to indicate it was an unknown type of radiation. The name stuck, although (over Röntgen's objections), many of his colleagues suggested calling them Röntgen rays. They are still referred to as Röntgen rays in some countries.
Uses
X-rays are highly penetrating of many materials, and are used in medicine to take pictures of bones and teeth. This is because bones absorb the radiation more than the less-dense soft tissue. X-rays from a source are passed through the body and onto a photographic plate; areas where radiation is absorbed show up as white and can be used to show broken or fractured bones. For imaging the digestive system, barium is swallowed.
Exposure to X-ray radiation is dangerous and cancer causing, so radiographers try to keep exposure to the patient to a minimum. Radiographers themselves wear lead aprons or stay behind a lead screen.
Diffraction of X-rays in chemistry can be used to investigate the structures of crystals and other structures - X-ray crystallography.
X-ray Astronomy is the study of the universe by analyzing the X-ray radiation which we receive on the earth.
Some lasers use on X-rays.
X-ray is also the letter X in the NATO phonetic alphabet.
had been watching in silence the flaming orange of the sunset above the
waiting.
"Honora, what do you say to going back to Grenoble?"
She succeeded in smiling at him.
"Whenever you like, Hugh," she said.
So the bowsprit of the 'Adhemar' was turned homewards; and with every
seemed to grow.
"I can't wait to show it to you, Honora--to see you in it," he exclaimed.
CHAPTER XII
THE ENTRANCE INTO EDEN
They had travelled through the night, and in the early morning left the
smaller train with parted lips and beating heart, gazing now and again at
Chiltern was like a schoolboy.
"We'll soon be there," he cried, but it was nearly nine o'clock when they
Chiltern line, he told her, and she was already within the feudal domain.
of upturned, staring faces, and for the moment her courage failed her.
backed up against the boards. The footman touched his hat, the grey-
a quick trot, Honora saw that the group on the station platform had with
windows.html">windows and lively signs, and already bustling with the business of the
that spanned a rushing stream confined between the foundation walls of
with windows wide open, and within them Honora heard the clicking and
Life was a strange thing that they should be doing this while she should
she read the legend Chiltern and Company.
"They still keep our name," said Hugh, "although they are in the trust."
He pointed out to her, with an air of pride, every landmark by the
shared with her. And he spoke of the times--as child and youth, home
to the left, behind the mills, threaded a village of neat wooden houses
.
On
wordlookup.net
All is still licensed under the GNU FDL.
It uses material from the wikipedia.
|
|