How does an X-ray machine work?

An X-ray is a shadow made of light you can't see. An X-ray machine heats a tungsten filament until electrons boil off, then pulls them across a vacuum with 40,000 to 150,000 volts. They slam into a spinning tungsten disc, and the sudden braking throws out X-ray photons.

Read how it works: How does an X-ray machine work? · The history of the X-ray machine · More boxes on Glassbox

Chapters in this interactive model

1. Inside an X-ray room: A tube that fires electrons at metal, a beam, a patient and a detector.
2. Making X-rays: Boil electrons off a hot wire, fling them at tungsten, and 1% of the crash comes out as X-rays.
3. Why bones show up: An X-ray picture is a shadow: bone blocks more of the beam than muscle, and air blocks almost none.
4. From film to flat panel: X-rays are turned into light, then into a picture: chemically, with a laser, or with millions of tiny photodiodes.
5. How much radiation?: Doses are measured in millisieverts. A chest X-ray is about the same as a few days of natural background.
6. X-rays beyond the hospital: Airport scanners, cracks in welds, and the shapes of molecules like DNA.