X-rays were discovered accidentally in 1895 by the German physicist Wilhelm Roentgen. He was working with a cathode ray tube when he noticed an unexpected glow about two metres from the tube, coming from some barium platinocyanide (a fluorescent material). Given that the cathode ray tube was in a black cardboard box, the cathode rays could not have reached the fluorescent material. Clearly a more penetrating radiation was responsible. Not yet knowing what kind of rays they were, he called them x-rays.
When
he placed his ha
nd in their path he found that
human flesh is transparent to x-rays but that
bones are not.
Roentgen soon found that photographic plates were sensitive to the newly discovered rays. He convinced his wife to participate in an experiment. When the image of Bertha's hand was developed, the bones of her hand and the two rings she wore were clearly visible. She was horrified at the result, as she saw in the image a premonition of death.
The
picture of Bertha Roentgen's hand, taken on 22nd Dec.1895,
was soon displayed in newspapers and scientific publications
all over Europe and the United States.
It is probably hard for us to imagine today, how eerie this image was at the time. The fact that x-rays could reveal the skeleton within its case of flesh without any apparent harm, was startling. The interest it generated, triggered a good deal of research into x-rays and related effects. Doctors were quick to recognise the medical potential revealed in Roentgen's first x-ray of his wife's hand.
Before publishing
the photograph of Bertha’s hand, Roentgen investigated and
identified most of the properties of x-rays. In particular, he
identified
that x-rays
cause ionisation.
x-rays are unaffected by electric and magnetic fields
X-rays resembled cathode rays in so far as they both cause ionisation. However
cathode rays are deflected by electric and magnetic fields unlike x-rays.
| X-ray timeline | |
| 1895 | Roentgen identified most of the properties of x-rays |
| 1896 | The first clinical
use of x-rays when two British doctors used them to find a needle in a woman’s hand. |
| 1896 | The military first
used x-rays in Naples, to locate bullets in the forearms of two soldiers who had been wounded in Italy’s Ethiopian campaign. |
| 1899 | Haga and Wind noticed a slight broadening of an x-ray beam after it passed through a slit, a few thousandths of a millimetre wide, suggesting the possibility of diffraction if a narrow-enough slit could be found. |
| 1901 | Roentgen received the first Nobel prize for physics for his discovery. |
| 1906 | Barkla successfully polarized x-rays, confirming their wave nature. |
| 1906 | Beclere first used x-rays to diagnose a stomach disorder by first giving the patient a meal of bismuth. |
| 1907 | Mutation by x-ray reported in toads by Bardeen. |
| 1912 | Max von Laue predicted
and discovered that x-rays could be diffracted by crystals. |
| 1913 | Bragg successfully
analysed an x-ray diffraction pattern, which offered a major break through in crystallography. |
| 1913 | Hot cathode x-ray
tubes and tungsten targets permitting higher voltages, first introduced by Coolidge. |
| 1922 | Film
badges for
personnel monitoring ----- developed by G. Pfahler. |
| 1931 | Tomography developed |
| 1948 | First experimental x-ray image intensifier developed by Coltman. |
| 1972 | The CAT scanner (based on x-rays) was invented by Godfrey Hounsfield. |