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Photons and X-Rays

When Wilhelm Roentgen invented X-ray technology in 1895, medical science took a big leap. Doctors were now able to easily see broken bones, swallowed objects, and tooth decay. And today, modified X-rays can be used to see soft tissue as well.

Inside X-ray machine is a tube in which a target (anode) made of heavy atoms, such as tungsten is shot at by an electron gun (cathode) which sends high energy electrons to the target. Electrons are deflected and Voila! x-rays are produced. Because electrons are shot at a target and energy is released, making X-rays is like the photoelectric effect in reverse.

X-Rays are carried by photons like any other form of electromagnetic radiation. We can't see them because, unlike light, our eyes are not sensitive to the shorter wavelength of X-rays.

There are two ways to make X-ray photons:

All of the collisions in the tube make the machine very hot so a motor rotates the anode to keep it cool. Lead covers the whole machine to keep the radiation from going everywhere. There is a small window in the lead though, that lets a beam of the X-ray photons escape. On the other side of the patient a camera records the pattern of the x-rays that pass through the body. The camera is just like any normal film camera, except X-ray light sets it off instead of visible light.

When a high energy X-ray photon collides with an electron, the Compton effect occurs. The photon and the electron are deflected at an angle, and because the photon transferred some energy to the electron, the photon comes out of the collision with a longer wavelength. The longer the wavelength, the bigger the angle. Compton scattering is what we call the collisions and the change of wavelength. The Compton effect usually occurs with high energy X-rays and low atomic numbers.

Moseley did a lot of work with X-rays, but here's one equation of his is used to find frequency of x-rays from the L-shell:

Let's try a problem using this equation. An X-ray machine uses the k-shell technique to produce X-rays. It's target is made of tungsten (W). What is the frequency of the X-rays emitted from the L-shell? v = (5/36)cR(Z - 1)2
v = (5/36)(2.998x108)(1.09768x107)(74-1)2
v = 2.44x1018Hz

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Elona Turley

A quantum of electromagnetic radiation.

Tungsten (W):
Atomic number - 74
Atomic weight - 183.84
also called Wolfram

Electromagnetic Radiation
Energy resulting from the acceleration of electric charge and the associated electric fields and magnetic fields.

Henry G. J. Moseley:
British physicist and chemist
Used x-ray spectra to study atomic structure
Was killed in World War I

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