Among other things, the charge can break DNA chains.
#The rays produced in a cathode tube are free#
Free electrons then collide with other atoms to create more ions.Īn ion's electrical charge can lead to unnatural chemical reactions inside cells. But when an X-ray hits an atom, it can knock electrons off the atom to create an ion, an electrically charged atom. When normal light hits an atom, it can't change the atom in any significant way. The problem is that X-rays are a form of ionizing radiation. Doctors can bring different materials into focus by varying the intensity of the X-ray beam. Hard material, such as bone, appears white, and softer material appears black or gray. That is, the areas that are exposed to more light appear darker and the areas that are exposed to less light appear lighter. Generally, doctors keep the film image as a negative. (See How Photographic Film Works to learn about this process.) The X-ray camera uses the same film technology as an ordinary camera, but X-ray light sets off the chemical reaction instead of visible light.
#The rays produced in a cathode tube are series#
The beam passes through a series of filters on its way to the patient.Ī camera on the other side of the patient records the pattern of X-ray light that passes all the way through the patient's body. A small window in the shield lets some of the X-ray photons escape in a narrow beam. This keeps the X-rays from escaping in all directions. The entire mechanism is surrounded by a thick lead shield. A cool oil bath surrounding the envelope also absorbs heat. A motor rotates the anode to keep it from melting (the electron beam isn't always focused on the same area). The high-impact collisions involved in X-ray production generate a lot of heat. This "braking" action causes the electron to emit excess energy in the form of an X-ray photon.
Like a comet whipping around the sun, the electron slows down and changes direction as it speeds past the atom. An atom's nucleus may attract a speeding electron just enough to alter its course. In the next section, we'll see how X-ray machines put this effect to work.įree electrons can also generate photons without hitting an atom. The calcium atoms that make up your bones are much larger, so they are better at absorbing X-ray photons. The soft tissue in your body is composed of smaller atoms, and so does not absorb X-ray photons particularly well. Smaller atoms, where the electron orbitals are separated by relatively low jumps in energy, are less likely to absorb X-ray photons. A larger atom is more likely to absorb an X-ray photon in this way, because larger atoms have greater energy differences between orbitals - the energy level more closely matches the energy of the photon. Some of the energy from the X-ray photon works to separate the electron from the atom, and the rest sends the electron flying through space. They can, however, knock an electron away from an atom altogether. X-ray photons also pass through most things, but for the opposite reason: They have too much energy. Radio waves don't have enough energy to move electrons between orbitals in larger atoms, so they pass through most stuff. The energy level of the photon fits with various energy differences between electron positions. The atoms that make up your body tissue absorb visible light photons very well. Immediately after discovering X-rays themselves, he had discovered their most beneficial application.
Finally, he put his hand in front of the tube, and saw the silhouette of his bones projected onto the fluorescent screen. Roentgen placed various objects between the tube and the screen, and the screen still glowed. Roentgen assumed this would have blocked most of the radiation. This response in itself wasn't so surprising - fluorescent material normally glows in reaction to electromagnetic radiation - but Roentgen's tube was surrounded by heavy black cardboard. Roentgen noticed that a fluorescent screen in his lab started to glow when the electron beam was turned on. In 1895, a German physicist named Wilhelm Roentgen made the discovery while experimenting with electron beams in a gas discharge tube. Science & Society Picture Library/SSPL via Getty ImagesĪs with many of mankind's monumental discoveries, X-ray technology was invented completely by accident. This X-ray is of the hands of Queen Mary and King George and was taken just a year after the monumental and accidental discovery of X-rays in 1895.