Chapter 4: Q23P (page 170)
In Problem4.3 you showed that . Apply the raising operator to find localid="1656065252558" . Use Equation 4.121to get the normalization.
Short Answer
The value of.
Chapter 4: Q23P (page 170)
In Problem4.3 you showed that . Apply the raising operator to find localid="1656065252558" . Use Equation 4.121to get the normalization.
The value of.
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Get started for free[Refer to Problem 4.59 for background.] In classical electrodynamics the potentials Aandare not uniquely determined; 47 the physical quantities are the fields, E and B.
(a) Show that the potentials
(whereis an arbitrary real function of position and time). yield the same fields asand A. Equation 4.210 is called a gauge transformation, and the theory is said to be gauge invariant.
(b) In quantum mechanics the potentials play a more direct role, and it is of interest to know whether the theory remains gauge invariant. Show that
satisfies the Schrödinger equation (4.205) with the gauge-transformed potentialsand, Sincediffers fromonly by a phase factor, it represents the same physical state, 48and the theory is gauge invariant (see Section 10.2.3for further discussion).
(a) For a functionthat can be expanded in a Taylor series, show that (where is an arbitrary angle). For this reason, is called the generator of rotations about the Z-axis. Hint: Use Equation , and refer Problem .More generally, is the generator of rotations about the direction , in the sense that effects a rotation through angle (in the right-hand sense) about the axis . In the case of spin, the generator of rotations is . In particular, for spin tells us how spinors rotate.
(b) Construct the matrix representing rotation by about the X-axis, and show that it converts "spin up" into "spin down" , as you would expect.
(c) Construct the matrix representing rotation by about the Y-axis, and check what it does to
(d) Construct the matrix representing rotation by about the -Zaxis, If the answer is not quite what you expected, discuss its implications.
(e) Show that
Use equations 4.27 4.28 and 4.32 to constructCheck that they are normalized and orthogonal
A hydrogen atom starts out in the following linear combination of the stationary states n=2, l=1, m=1 and n=2, l=1, m=-1.
(a) ConstructSimplify it as much as you can.
(b) Find the expectation value of the potential energy,. (Does it depend on t?) Give both the formula and the actual number, in electron volts.
Because the three-dimensional harmonic oscillator potential (Equation 4.188)is spherically symmetric, the Schrödinger equation can be handled by separation of variables in spherical coordinates, as well as cartesian coordinates. Use the power series method to solve the radial equation. Find the recursion formula for the coefficients, and determine the allowed energies. Check your answer against Equation4.189.
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