S10P1CLec27B

S10P1CLec27B - Physics 1C Lecture 27B"In quantum mechanics...

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Physics 1C Lecture 27B "In quantum mechanics we have found a region of the universe where the human brain is simply unable to be comfortable." --James Trefil

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X-Rays X-rays are electromagnetic radiation with short wavelengths (~0.1nm). X-rays have the ability to penetrate most materials. X-rays are produced when high-speed electrons are suddenly slowed down. This slow down can be caused by striking a metal target. The key point to remember is that any time a charged particle is accelerated it will emit electromagnetic radiation.
X-Ray Scattering If you shoot a beam of X-rays at a crystal onto a photographic film, the diffracted radiation will have sections of high intensity. These sections correspond to constructive interference. This array of spots is called a von Laue pattern. Since X-rays are just a form of light, these spots are caused by a path length difference.

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X-Ray Scattering For diffraction to occur, the spacing between the lines must be approximately equal to the wavelength of the radiation to be measured. The crystal structure is determined by analyzing the positions and intensities of the various spots.
Bragg’s Law The beam reflected from the lower surface travels farther than the one from the upper surface. If the path length difference equals some integral multiple of the X-ray wavelength, you will get constructive interference. Bragg’s Law gives the conditions for constructive interference: 2 d sin θ = m λ where m = 1, 2, 3...

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The Compton Effect In 1923, Arthur Compton directed a beam of X- rays toward a block of graphite He detected the scattered X-rays had a slightly longer wavelength than the incident X-rays.
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