Ch 39 Relevant Concept Questions

Ch 39 Relevant Concept Questions - eV. Does a photon of...

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University Physics Young and Freedman Chapter 39 Concept Questions and solutions Chapter 39: Pre-Chapter Question Q: A TV picture tube uses a fast-moving beam of electrons to create an image on the screen. Can you see the wave aspect of these electrons when you look at the screen? A: Use Eq. 39.4 to find the wavelength, which comes to 8.7 x 10^-12 m, which is too small to see. 1. A proton has a slightly smaller mass than a neutron. Compared to the neutron described in Ex. 39.1, would a proton of the same wavelength have more or less kinetic energy? For a given wavelength, the kinetic energy is inversely proportional to the mass (Example 39.1), so the proton has more kinetic energy than a neutron. 2. Ex. 39.2 shows that to give electrons a wavelength of 1.7 x 10^-10 m, they must be accelerated from the rest through a voltage of 54 V and so acquire a kinetic energy of 54
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Unformatted text preview: eV. Does a photon of this same energy also have a wavelength of 1.7 x 10^-10 m? E = hf and f = c/λ, so λ = hc/E = 2.3 x 10^-8 m; more than 100x greater than the wavelength of an electron of the same energy. 3. Absolute zero is the temperature at which molecular motion is at an absolute minimum. Use the Heisenberg uncertainty principle to explain why there must be some molecular motion even at T = 0 K. No, if no movement there would be zero uncertainty in its position. Heisenberg states this can never be zero. 4. N/A 5. Does a wave packet given by Eq. 39.25 represent a stationary state? It does not represent a state of indefinite energy and therefore not a stationary state. See page 1535 for more information....
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This note was uploaded on 04/18/2008 for the course PHYS 0030 taught by Professor Cutts during the Spring '07 term at Brown.

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