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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

Short Answer

Expert verified

The transmission coefficient equation is,T=11+sin2(2a2m(EV0)h2)(V024E(E+V0))

Step by step solution

01

 Define the Schrodinger 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 Schrodinger equation

Csin(la)+Dcos(la)=Feika 鈥(颈)

l(Ccos(la)Dsin(la))=ikFeika

Ccos(la)Dsin(la)=iklFeika 鈥(颈颈)

k=2mEh2 l=2m(E=V0)h2

Csin2(la)+Dcos(la)sin(la)=Feikasin(la)Multiply both sides sin(la)

Ccos2(la)Dcos(la)sin(la)=iklFeikacos(la)Multiply both sides cos(la)

Add the above 2 equations

C=Fsin(la)+iklcos(la)eika 鈥(颈颈颈)

Now equation (i) multiply withwe get an equation (ii) multiply with sin(la)

Csin(la)cos(la)+Dcos2(la)=Fsin(la)eika

Ccos2(la)Dcos(la)sin(la)=iklFeika

03

Find the Schrodinger equation

Now add the above equation

D=Fcos(la)iklsin(la)eika 鈥(颈惫)

Substitute equations (iii) and (iv)

Aeika+Beika=Csin(la)+Dcos(la)

Put values of Cand D

Aeika+Beika=F(sin(la)+iklcos(la))eika(sin(la))+F(cos(la)iklsin(la))eikacos(la)

Aeika+Beika=Fcos(2la)iklsin(2la)eika 鈥(惫)

ik[AeikaBeika]=lCcos(la)iklsin(la)

ik[AeikaBeika]=likF(sin(la)+iklcos(la))eika(cos(la))+F(cos(la)iklsin(la))eikasin(la))]

role="math" localid="1656056140172" ikAeikaBeika=Fcos(2la)ilksin(2la)eika 鈥(惫颈)

2Beika=Fcos(2la)iklsin(2la)eikaFcos(2la)ilksin(2la)eika

2Beika=iFl2k2lksin(2la)eika

B=iFl2k22lksin(2la)

04

Solve the terms C and D

2Aeika=F2cos(2la)lkl+lksin(2la)eika

F=Ae2ikacos(2la)+ik2+l22klsin(2la)

FA=e2ikacos(2la)+ik2+l22klsin(2la)

T=FA2

role="math" localid="1656056446552" T=e2ikacos(2la)+ik2+l22klsin(2la)2

T=e2ikacos(2la)+ik2+l22klsin(2la)e2ikacos(2la)ik2+l22klsin(2la)

By putting cos2(2la)=1sin2(2la)

T=11+sin2(2la)(k2l2)24k2l2

T=11+sin22a2m(EV0)h2V024E(E+V0)

Where

l=2m(EV0)h2,k=2mEh2

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Most popular questions from this chapter

A particle in the infinite square well (Equation 2.22) has the initial wave function 唯 (x, 0) = A sin3(蟺x/a) (0 鈮 x 鈮 a). Determine A, find 唯(x, t), and calculate 銆坸銆塧s a function of time. What is the expectation value of the energy? Hint: sinn胃 and cosn胃 can be reduced, by repeated application of the
trigonometric sum formulas, to linear combinations of sin(m胃) and cos(m胃), with m = 0, 1, 2, . . ., n.

Solve the time-independent Schr 虉odinger equation for a centered infinite square well with a delta-function barrier in the middle:

V(x)={伪未(x)for-a<x<+afor|x|a

Treat the even and odd wave functions separately. Don鈥檛 bother to normalize them. Find the allowed energies (graphically, if necessary). How do they compare with the corresponding energies in the absence of the delta function? Explain why the odd solutions are not affected by the delta function. Comment on the limiting cases 伪 鈫 0 and 伪 鈫 鈭.

Show that there is no acceptable solution to the Schrodinger equation for the infinite square well with E=0orE<0(This is a special case of the general theorem in Problem 2.2, but this time do it by explicitly solving the Schrodinger equation, and showing that you cannot meet the boundary conditions.)

-consider the 鈥渟tep鈥 potential:

v(x)={0,ifx0,V0,ifx>0,

a.Calculate the reflection coefficient, for the case E < V0, and comment on the answer.

b. Calculate the reflection coefficient, for the case E >V0.

c. For potential such as this, which does not go back to zero to the right of the barrier, the transmission coefficient is not simply F2A2(with A the incident amplitude and F the transmitted amplitude), because the transmitted wave travels at a different speed . Show thatT=E-V0V0F2A2,for E >V0. What is T for E < V0?

d. For E > V0, calculate the transmission coefficient for the step potential, and check that T + R = 1.


A particle in the infinite square well has the initial wave function

(X,0)={Ax,0xa2Aa-x,a2xa

(a) Sketch (x,0), and determine the constant A

(b) Find(x,t)

(c) What is the probability that a measurement of the energy would yield the valueE1 ?

(d) Find the expectation value of the energy.

See all solutions

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