Barium platinocyanide glowing across a darkened laboratory from a discharge tube wrapped in black card (1895)
Röntgen's accidental observation at Würzburg on 8 November 1895
Science · Medicine & the body
The X-ray
Discovered 8 November 1895
Medicine — radiology and diagnostic imaging
Penetrating electromagnetic radiation of very short wavelength, discovered by Wilhelm Conrad Röntgen at Würzburg on 8 November 1895 when a screen coated in barium platinocyanide glowed across a darkened laboratory from a covered discharge tube. He named the rays with the algebraic symbol for an unknown, photographed his wife's hand within weeks, refused to patent anything, and received the first Nobel Prize in Physics in 1901. Within a year hospitals were using the rays to find fractures and bullets, and radiology became the first medical speciality to be created by a single piece of physics.
How to spot them
- ▸Würzburg, 8 November 1895, and a screen of barium platinocyanide glowing in the dark
- ▸The letter stands for an unknown; in German-speaking countries the rays are named after their discoverer
- ▸The very first Nobel Prize in Physics, 1901
- ▸Wavelengths of roughly 0.01 to 10 nanometres — between ultraviolet and gamma rays
- ▸Computed tomography: Hounsfield at EMI and Cormack, Nobel Prize 1979
Key facts
A photograph of Anna Bertha Ludwig's hand, wedding ring and all, taken in December 1895 (1895)
Röntgen's wife, who is said to have exclaimed that she had seen her own death
The letter its discoverer chose because he did not know what it was
X for the algebraic unknown; German usage prefers his own name instead
The very first Nobel Prize in Physics, awarded in 1901 (1901)
Röntgen donated the money to his university and refused to patent the discovery
Godfrey Hounsfield's EMI machine and Allan Cormack's mathematics, honoured in 1979 (1979)
Computed tomography — the first clinical scan was at Atkinson Morley Hospital in 1971
A barium meal, a mammogram and a chest film
Three everyday diagnostic uses, one of them with a contrast medium
Clarence Dally, Edison's assistant, and the early operators who lost hands and then their lives (1904)
The first generation had no idea the radiation was dangerous
The mobile units Marie Curie drove to the Western Front, nicknamed 'petites Curies' (1914)
Battlefield radiography for locating shrapnel and setting fractures
Key ideas
- They are produced by slamming fast electrons into a metal target: most of the radiation is bremsstrahlung from electrons being decelerated, with sharp characteristic lines from the target element on top.
- A radiograph is a shadow, not a picture: dense tissue such as bone absorbs more radiation, so the image is a map of absorption, which is why soft tissues need a contrast medium to show up.
- Because the wavelength is comparable to the spacing between atoms in a crystal, the same radiation that images a broken wrist can also reveal molecular structure by diffraction.
Quick-fire facts
- •Discovered by Wilhelm Conrad Röntgen at the University of Würzburg on 8 November 1895; his paper 'Über eine neue Art von Strahlen' appeared on 28 December
- •The first published radiograph was of the hand of his wife, Anna Bertha Ludwig
- •Röntgen won the first Nobel Prize in Physics in 1901 and refused to take out any patent
- •Wavelengths run roughly from 0.01 to 10 nanometres, between ultraviolet and gamma radiation
- •Produced when high-speed electrons strike a metal target, giving bremsstrahlung plus characteristic lines
- •Max von Laue won the 1914 Nobel Prize for diffraction by crystals; William Henry and William Lawrence Bragg shared the 1915 prize, the son being the youngest ever physics laureate at 25
- •Godfrey Hounsfield and Allan Cormack shared the 1979 Nobel Prize in Physiology or Medicine for computed tomography; the Hounsfield unit measures radiodensity
- •Element 111, roentgenium, is named after the discoverer, as is the obsolete unit of exposure
- •Absorbed dose is measured in grays and equivalent dose in sieverts
- •Clarence Dally, Thomas Edison's assistant, died in 1904 from radiation injuries, one of the first known victims
- •Marie Curie equipped mobile radiography vehicles, the 'petites Curies', for the French army in the First World War
- •Contrast media such as barium sulphate and iodinated compounds make soft tissues and vessels visible
Drill it — 9 cards
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Sources
- The Nobel Foundation — The Nobel Prize in Physics 1901
- NHS — X-ray
- The Nobel Foundation — The Nobel Prize in Physiology or Medicine 1979