practice_1a.pdf

# practice_1a.pdf - Physics 240/250 Practice Midterm 1A#1...

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Physics 240/250 Practice Midterm 1A #1) When light with wavelength 327 nm is incident upon the surface of a certain metal, the maximum kinetic energy of the ejected electrons is 0.90 eV. Is the metal one of those in the table below? If so, which? Element Density Atomic Work Function Melting Point Year (g/cm 3 ) Number (eV) (K) Discovered Be 1.85 4 5.00 2742 1798 Na 0.97 11 2.28 371 1807 Mg 1.74 12 3.68 923 1755 K 0.86 19 2.30 337 1807 Ca 1.55 20 2.90 1115 1808 1

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#2 X-rays scatter from a set of crystal planes. The scattering angles from two successive orders of reflection are 2 θ = 66 . 20 and 2 θ = 93 . 46 . a) What are all the possible scattering angles from this set of planes? Give your answers to this problem to 4 significant figures (two digits after the decimal point). Hint: you do not need to know either the x-ray wavelength or the distance between the planes. 2
b) If the wavelength of the x-rays in part (a) is 0 . 154 nm, what is the spacing between the planes?

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