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The product of uncertainties in particle's momentum and position.

Short Answer

Expert verified

The product of uncertainty in position and momentum is according to the uncertainty principle.

Step by Step Solution

The complete rule stipulates that the product of the uncertainties in position and velocity is Planck's constant, or about6.6×10-34 joule-second.

Step by step solution

01

The concept and the formula used.

The uncertainty in position isL112-12n2π2 .

The uncertainty in momentum is nhxL.

Formula used:

The uncertainty principle states that the position and momentum of an atom cannot be measured simultaneously. It gives uncertainty in position if we have uncertainty in momentum.

Write the expression for the uncertainty principle.

ΔxΔpA2

Here, Δxis the change in position,Δp is the change in momentum and h is the reduced Planck's constant.

02

Calculating the value using the formul

Write the expression for uncertainty in position.

Δx=L112-12n2x2...(1)

Here,Δxis the uncertainty in position, L is the length and n is the number of state.

Write the expression for uncertainty in momentum.

Δp=nλ^πL..(2)

Here,Δpis the uncertainty in momentum, n is the number of orbit and L is length.

Multiply equations (1) and (2).

ΔxΔp=nπ112-12n2π2

=n2π212-122

For ground state, n=1the product of uncertainties is bigger thann2, that meansΔxΔpn2which is according to the uncertainty principle for position and momentum operator.

Thus, the product of uncertainty in position and momentum is according to uncertainty principle.

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Most popular questions from this chapter

There are mathematical solutions to the Schrödinger equation for the finite well for any energy, and in fact. They can be made smooth everywhere. Guided by A Closer Look: Solving the Finite Well. Show this as follows:

(a) Don't throw out any mathematical solutions. That is in region Il (x<0), assume that (Ce+ax+De-ax), and in region III (x>L), assume thatψ(x)=Fe+ax+Ge-ax. Write the smoothness conditions.

(b) In Section 5.6. the smoothness conditions were combined to eliminate A,Band Gin favor of C. In the remaining equation. Ccanceled. leaving an equation involving only kand α, solvable for only certain values of E. Why can't this be done here?

(c) Our solution is smooth. What is still wrong with it physically?

(d) Show that

localid="1660137122940" D=12(B-kαA)andF=12e-αL[(A-Bkα)sin(kL)+(Akα+B)cos(kL)]

and that setting these offending coefficients to 0 reproduces quantization condition (5-22).

Equation (5 - 16) gives infinite well energies. Because equation (5 - 22) cannot be solved in closed form, there is no similar compact formula for finite well energies. Still many conclusions can be drawn without one. Argue on largely qualitative grounds that if the walls of a finite well are moved close together but not changed in height, then the well must progressively hold fewer bound states. (Make a clear connection between the width of the well and the height of the walls.)

equation (5-33). The twosolutionsare added in equal amounts. Show that if we instead added a different percentage of the two solutions. It would not change the important conclusion related to the oscillation frequency of the charge density.

For the harmonic oscillator potential energy, U=12kx2, the ground-state wave function is ψ(x)=Ae-(mk/2)x2, and its energy is 12k/m.

(a) Find the classical turning points for a particle with this energy.

(b) The Schrödinger equation says that ψ(x) and its second derivative should be of the opposite sign when E > Uand of the same sign when E < U . These two regions are divided by the classical turning points. Verify the relationship between ψ(x)and its second derivative for the ground-state oscillator wave function.

(Hint:Look for the inflection points.)

It is possible to take the finite well wave functions further than (21) without approximation, eliminating all but one normalization constant C . First, use the continuity/smoothness conditions to eliminate A, B , andG in favor of Cin (21). Then make the change of variables z=x-L/2 and use the trigonometric relations

sin(a+b)=sinacosb+cosasinband

cos(a+b)=cosacosb-sinasinbon the

functions in region I, -L/2<z<L/2. The change of variables shifts the problem so that it is symmetric about z=0, which requires that the probability density be symmetric and thus that ψ(z)be either an odd or even function of z. By comparing the region II and region III functions, argue that this in turn demands that (α/k)sinkL+coskL must be either +1 (even) or -1 (odd). Next, show that these conditions can be expressed, respectively, as αk=tankL2 and αk=-cotkL2. Finally, plug these separately back into the region I solutions and show that

ψ(z)=C×{eα(z+L/2)          z<L/2coskzcoskL2          -L/2<z<L/2e-α(z-L/2)          z>L/2


or

ψ(z)=C×{eα(z+L/2)          z<L/2-sinkzsinkL2          -L/2<z<L/2e-α(z-L/2)          z>L/2

Note that Cis now a standard multiplicative normalization constant. Setting the integral of |ψ(z)|2 over all space to 1 would give it in terms of kand α , but because we can’t solve (22) exactly for k(or E), neither can we obtain an exact value for C.

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