Chapter 7: Q42E (page 281)
In Appendix G. the operator for the square of the angular momentum is shown to be
Use this to rewrite equation (7-19) as
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Chapter 7: Q42E (page 281)
In Appendix G. the operator for the square of the angular momentum is shown to be
Use this to rewrite equation (7-19) as
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An electron is in anI = 3state of the hydrogen atom, what possible angles might the angular momentum vector make with the z-axis.
Question: An electron is trapped in a cubic 3D well. In the states = (a) (2,1,1) (b) (1,2,1)(c) (1,1,2), what is the probability of finding the electron in the region . Discus any difference in these results.
Classically, an orbiting charged particle radiates electromagnetic energy, and for an electron in atomic dimensions, it would lead to collapse in considerably less than the wink of an eye.
(a) By equating the centripetal and Coulomb forces, show that for a classical charge -e of mass m held in a circular orbit by its attraction to a fixed charge +e, the following relationship holds
.
(b) Electromagnetism tells us that a charge whose acceleration is a radiates power . Show that this can also be expressed in terms of the orbit radius as . Then calculate the energy lost per orbit in terms of r by multiplying the power by the period and using the formula from part (a) to eliminate .
(c) In such a classical orbit, the total mechanical energy is half the potential energy, or . Calculate the change in energy per change in r : . From this and the energy lost per obit from part (b), determine the change in per orbit and evaluate it for a typical orbit radius of . Would the electron's radius change much in a single orbit?
(d) Argue that dividing by P and multiplying by dr gives the time required to change r by dr . Then, sum these times for all radii from to a final radius of 0. Evaluate your result for . (One limitation of this estimate is that the electron would eventually be moving relativistically).
Mathematically equation (7-22) is the same differential equation as we had for a particle in a box-the function and its second derivative are proportional. Butfor m1= 0is a constant and is allowed, whereas such a constant wave function is not allowed for a particle in a box. What physics accounts for this difference?
Verify that the solution given in equation (7.6) satisfy differential equations (7.5) as well as the required boundary conditions.
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