PROBLEM 45 &amp; 46 May 21 2010

# PROBLEM 45 &amp; 46 May 21 2010 - 2 E U m p About how...

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Solving Problems 45 and 46 Phys 002C May 21 2010 Problem 45. (Like Problem 28.34) The hydrogen 2P level decays with a 1.6 ns lifetime to the 1S level emitting Lyman radiation at 123 nm. What is the approximate line width of the Lyman radiation? (a) 1 nm; (b) 0.01 nm; (c) 0.00001 nm; (d) 0.1 nm; (e) 0.001 nm. What do you know?  / ) / ( ) / ( ) / ( ) ( / 2 hc hc hc h t h E So = (123 10 t c / 2 -9 ) 2 /(3 10 8 1.6 10 -9 )=3.15 10 -14 m = 3.15 10 -5 nm Problem 46. (Like Problem 28.49) The probability of a particle of energy E getting through a tunnel barrier of width and potential height U in a single try is x } 2 exp{ x , where 2 / ) (
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Unformatted text preview: 2 / E U m p . About how many times would an electron of total energy E =1 eV have to hit a barrier of width =1 nm and height U = 2 eV, before tunneling through? Note, the electron mass is 0.911×10 x -30 kg, 1 eV=1.602×10-19 J and =1.054×10-34 J·s. (a) 1; (b) 86; (c) 2,500; (d) 28,000; (e) 64,000,000 What do you know? 2 . 10 10 054 . 1 / 10 6 . 1 10 911 . 2 10 2 / ) ( 2 2 2 34 19 30 9 2 Js J kg m E U m x x The number of tries would need to be exp{10.2} = 28,000....
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