Normalize ψ(x)the equation 2.151, to determine the constants D and F.

Short Answer

Expert verified

D=1a+1k

F=ekacoslaa+1k

Step by step solution

01

 Define the Schrödinger equation

A differential equation describes matter in quantum mechanics in terms of the wave-like properties of particles in a field. Its answer is related to a particle's probability density in space and time.

02

Determine the Constants

=20|ψ|2dx=2|D|20acos2lx+|F|20e2kxdx

=2|D|2x2+14lsin2lx|0a+||F|212ke2kx|a2[|D|2a2+sin2la4l+|F|2e2ka2k

But F=Dekacosla(Eq2.152), so role="math" localid="1656054797733" 1=|D|2a+sin(2la)2l+cos2(la)k

Furthermore k=ltan(la)(Eq.2154), so

=|D|2a+2sinlacosla2l+cos3lalsinla

=|D|2a+coslalsinla(sin2la+cos2la)

=|D|2a+1ltanla

=|D|2a+1k

D=1a+1k

F=ekacoslaa+1k

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Most popular questions from this chapter

a) Show that the wave function of a particle in the infinite square well returns to its original form after a quantum revival time T = 4ma2/π~. That is: Ψ (x, T) = Ψ (x, 0) for any state (not just a stationary state).


(b) What is the classical revival time, for a particle of energy E bouncing back and forth between the walls?


(c) For what energy are the two revival times equal?

For the wave function in Example 2.2, find the expectation value of H, at time t=0 ,the “old fashioned way:

H=Ψ(x,0)H^Ψ(x,0)dx.

Compare the result obtained in Example 2.3. Note: BecauseH is independent of time, there is no loss of generality in usingt=0

A particle in the infinite square well (Equation 2.22) has the initial wave function Ψ (x, 0) = A sin3(πx/a) (0 ≤ x ≤ a). Determine A, find Ψ(x, t), and calculate 〈x〉as a function of time. What is the expectation value of the energy? Hint: sinnθ and cosnθ can be reduced, by repeated application of the
trigonometric sum formulas, to linear combinations of sin(mθ) and cos(mθ), with m = 0, 1, 2, . . ., n.

The gaussian wave packet. A free particle has the initial wave function

Y(x,0)=Ae-ax2

whereAand are constants ( is real and positive).

(a) NormalizeY(x,0)

(b) Find Y(x,t). Hint: Integrals of the form

-+e-(ax2+bx)dx

Can be handled by “completing the square”: Lety=a[x+bl2a], and note that(ax2+bx)=y2-(b2l4a). Answer:

localid="1658297483210" Y(x,t)=(2aπ)1/4e-ex2l[1+(2ihatlm)]1+(2ihatlm)

(c) Find . Express your answer in terms of the quantity

localid="1658297497509" ω=a1+(2ihatlm)2

Sketchlocalid="1658124147567" |Y|2(as a function of x) at t=0, and again for some very large t. Qualitatively, what happens to |Y|2, as time goes on?

(d) Find <x>,<p>,<x2>,<p2>,σxand σP. Partial answer:localid="1658297458579" <p2>=ah2, but it may take some algebra to reduce it to this simple form.

(e) Does the uncertainty principle hold? At what time tdoes the system come

closest to the uncertainty limit?

Derive Equations 2.167 and 2.168.Use Equations 2.165 and 2.166 to solve C and D in terms of F:

C=(sin(la)+iklcos(la))eikaF;D=(cos(la)iklsin(la))eikaF

Plug these back into Equations 2.163 and 2.164. Obtain the transmission coefficient and confirm the equation 2.169

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