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Unformatted text preview: Lesson 5.1 Homework Solutions 1. What is the de Broglie wavelength for (i) an electron, (ii) a proton both moving with a velocity of 100 m.s1 ? 34 6311 6.63 10 J.s ( ) 7.28 10 m 9.11 10 kg 100 m.s h i mv  = = = 34 9271 6.63 10 J.s ( ) 3.97 10 m 1.672 10 kg 100 m.s h ii mv  = = = 2. Calculate the de Broglie wavelength of a 70kg man running at 2.0 m.s1 . 34 361 6.63 10 J.s 4.7 10 m 70 kg 2 m.s h mv  = = = 3. A proton and an electron are accelerated from rest through a potential difference V. What is the ratio of the de Broglie wave length of an electron to that of a proton? The work done in accelerating an electron by a voltage V is W = eV. This becomes the kinetic energy of the electron such that m v 2 = eV 2 eV v m = 27 p31 e 2 / m 1.672 10 kg = = = 43 m 9.11 10 kg 2 / p p e p e e p p e e m eV m h h m v m v m eV m = = 4. An electron is accelerated from rest through a potential difference that gives it a matter wave with a wavelength of o.1 nm. What is the potential difference? The work done in accelerating an electron by a voltage V is W = eV. This becomes the kinetic energy of the electron such that m v 2 = eV 2 eV v m = 34 31 19 6.63 10 J.s 2 2 2 9.11 10 1.602 10 h h h mv eV meV V m m  = = = = ( 29 ( 29 ( 29 ( 29 34 9 31 19 2 34 2 9 31 19 2 34 2 31 19 9 6.63 10 J.s 0.1 10 2 9.11 10 1.602 10 6.63 10 J.s 0.1 10 2 9.11 10 1.602 10 6.63 10 J.s 151 V 2 9.11 10 1.602 10 0.1 10 V V V = = = = 5. Electrons are accelerated from rest through a potential of 250 kV. If the potential is increased to 600 kV, what is the ratio of the new de Broglie wavelength to the original? increased to 600 kV, what is the ratio of the new de Broglie wavelength to the original?...
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 Spring '11
 George
 Physics, Atom, Atomic Number, Electron, Work, Atomic orbital

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