102 lect26_handout

# 102 lect26_handout - Physics 102 Lecture 26 X-rays Make...

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Physics 102: Lecture 26, Slide 1 X-rays Physics 102: Lecture 26 Make sure your grade book entries are correct.

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Physics 102: Lecture 26, Slide 2 Photons with energy in approx range 100eV to 100,000eV . This large energy means they go right through you (except for your bones). What are the wavelengths? λ= hc E = 1240 eV nm E 1240 eV nm 100000 eV .01nm 1240 100 10 nm X-Rays .01 nm to 10 nm
Physics 102: Lecture 26, Slide 3 X-Ray Production • Black Body Radiation – Would require temperature over 10 times hotter than surface of sun • Excitation of outer electrons – Typically have energy around 10 eV • Radioactive Decays – Hard to turn on/off How do you produce 100 eV photons?

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Physics 102: Lecture 26, Slide 4 Electron Tubes • Accelerate an electron through a voltage difference to give it some energy. .. An electron is accelerated through a potential difference of 70,000 V. How much energy does it emerge with? Recall from Lecture 3: EPE = V q KE = EPE = (70,000 V) (1 e - ) = 1.6 x 10 -19 C = 70,000 eV = 11.2 x 10 -14 J EPE of voltage gap becomes K.E. for electron.
Physics 102: Lecture 26, Slide 5 From Electrons to X-Rays • Now take these high energy electrons (up to 100,000 eV) and slam them into heavy atoms - any element. • 2 kinds of X-Rays are produced: – “Bremsstrahlung” – “Characteristic”

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Physics 102: Lecture 26, Slide 6 Bremsstrahlung X-Rays Electron hits atom and slows down, losing kinetic energy.
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102 lect26_handout - Physics 102 Lecture 26 X-rays Make...

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