ProbSet2Solutions - Solutions to Problem Set 2 1.2 1.4...

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Solutions to Problem Set 2 1.2 radio waves < IR rays < visible light < UV rays 1.4 (a) 2.99792 x 10 8 m.s -1 = ( λ )(7.2 x 10 14 s -1 ) λ = (2.99792 x 10 8 m.s -1 )/(7.1 x 10 14 s -1 ) = 4.2 x 10 -7 m = 420 nm (b) 2.9972 x 10 8 m.s -1 ) = ( λ )(2.0 x 10 18 s -1 ) λ = (2.99792 x 10 8 m.s -1 )/(2.0 x 10 18 s -1 ) = 1.5 x 10 -10 m = 150 pm 1.12 (a) false. UV photons have higher energy than infrared photons. (b) false. The kinetic energy of the electron is directly proportional to the energy ( and hence frequency) of the radiation in excess of the amount of energy required to eject the electron from the metal surface. (c) true. 1.14 E work function = (4.37 eV)(1.6022 x 10 -19 J.eV -1 ) = 7.00 x 10 -19 J E kinetic = ½ mv2 = 0.5 (9.10939 x 10 -31 kg) ( 1.5 x 10 6 m.s -1 ) 2 = 1.02 x 10 -18 J E total = E work function + E kinetic = 1.72 x 10 -18 J E = h ν and c = νλ λ = hc/E = (6.626 x 10 -34 Js)(3.00 x 10 8 m.s -1 )/(1.72 x 10 -18 J) = 1.16 x 10 -7 m = 116 nm 1.18 mass of one He atom = Molar mass of He / Avogadro’s number = (4.00 g.mol -1 )/(6.022 x 10 23 atoms. mol -1 ) = 6.64 x 10 -24 g = 6.64 x 10 -27 kg From the de Broglie relationship, λ = h/mv = (6.626 x 10 -34 Js)/(6.64 x 10 -27 kg)(1230 m.s -1 ) = 8.11 x 10 -11 m 1.22 The observed line is the third lowest energy line. The frequency of the given line is
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ProbSet2Solutions - Solutions to Problem Set 2 1.2 1.4...

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