X-Rays Content from the guide to life, the universe and everything


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The following is a common procedure which is seen everyday all over the world. People run, fall, land in awkward and often painful positions, and break whatever bone(s) they landed awkwardly on. After that, normal people proceed to go to a doctor, who uses a device called an x-ray to examine the broken bone(s). The person is then put into a thin dress with no back, is given a large assortment of lead-filled clothing to put on, and is put in front of a machine which then hums. What the machine does, that you can't see, is pure science.

The Discovery of the X-Ray

The whole concept of the x-ray came from the physicist Wilhelm Conrad Roentgen, when he discovered in 1895 that electromagnetic radiation passed through most objects easily, but that it was absorbed by the bones of the human body. This was easily seen by placing a fluorescent screen nearby, which then illuminated.

How it Works

X-rays, or Roentgen Rays, are simply just that. They are high-energy photons emitted, usually, by a device made up of an electrode pair (an anode and a cathode), a glass vacuum tube, and a tungsten disk. When this device is switched on, the overall effect is that it flings electrons at a high speed with incredible force. These electrons reflect off the tungsten, and in the process lose an electron in a lower orbit. The effect of this is that the electrons above move down in the levels (much in the way that if you had five books, and took the bottom one off, the rest would take its place), and in the process, emits energy. This energy is electromagnetic radiation, known as x-rays.

The x-rays are nearly identical to the rays of light people are used to seeing - the only difference is the energy level, or wavelength, of the ray. Our eyes pick up the wavelength of natural light from our Sun. However, we cannot see into the infrared or the ultraviolet. Light rays and other forms of radiation are absorbed by the tissues in our bodies. X-rays, however, are not absorbed. They do not reflect, but pass through, and are absorbed. This is mostly by the calcium of the bones, but also by other types of tissue. This creates, when used in conjunction with the fluorescent screen, a form of a shadow, but one that shows the bones of the human body clearly. One can even be given injections of specific liquids that absorb the x-rays as so the veins and organs can be better seen.

And the Downside?

One problem that x-ray technology has, however, is the risk of radiation sickness. Normal light, when it collides with an atom, simply transfers energy, not doing any real harm, save skin cancer if one receives unprotected exposure to the Sun too often. However, x-rays behave differently. When an x-ray collides with an atom, it tends to bump off electrons, creating ions. The removed electrons collide with other atoms, creating even more ions. This in itself doesn't seem all too bad, but the problem comes into play when you take into account the ion's electrical charge. These electrical charges can cause uncontrolled chemical reactions, the most major of these being that it can break DNA strains. This will either kill the cell, or cause mutations. Such mutations can lead to cancer, birth defects, and other nasty problems. These mutations aren't a big worry for just one visit, but if one works around them all day, or if the examinee is pregnant, precautions are taken. This is why one is often equipped with lead-lined clothing, as lead doesn't easily permit rays to pass through it, acting as a sort of shield.

That's Not All, Folks

There is more to the use of x-rays than simply investigating broken bones. X-rays have many more medical functions, as well as numerous scientific applications. X-rays are now being used in cancer treatments, by exposing tumors to their radiation. Such cancerous growths can be killed by radiation treatments. In engineering, it can be used to examine metals and welds for defects, and also to identify different kinds of metal. This method is valuable because it allows for parts and products to be tested without destroying them. The only downside is that to use the x-ray in such a fashion, the emitter must be much more powerful, and therefore, more expensive. Using x-ray diffraction, the nature of microscopic elements can be found. In fact, several new elements have been discovered through the examination of x-ray spectra.

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