Uncertainty Principle
and
a particle in a Box

[Graphics:Images/SOL_PS4.p9.CHEM155_gr_1.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_2.gif]

Define the wave function

[Graphics:Images/SOL_PS4.p9.CHEM155_gr_3.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_4.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_5.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_6.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_7.gif]

a). - Calculate < x> and <[Graphics:Images/SOL_PS4.p9.CHEM155_gr_8.gif]>

[Graphics:Images/SOL_PS4.p9.CHEM155_gr_9.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_10.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_11.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_12.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_13.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_14.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_15.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_16.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_17.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_18.gif]

b). - Calculate < p> and <[Graphics:Images/SOL_PS4.p9.CHEM155_gr_19.gif]>

[Graphics:Images/SOL_PS4.p9.CHEM155_gr_20.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_21.gif]

Notice that Cos[2 n π] is equal to + 1 or -1 depending on n being  even or odd.  But the Cos function is squared

[Graphics:Images/SOL_PS4.p9.CHEM155_gr_22.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_23.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_24.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_25.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_26.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_27.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_28.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_29.gif]

c). - Calculate Δx Δp

[Graphics:Images/SOL_PS4.p9.CHEM155_gr_30.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_31.gif]

Consider the following function

[Graphics:Images/SOL_PS4.p9.CHEM155_gr_32.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_33.gif]

The minum value of f is f[1]

[Graphics:Images/SOL_PS4.p9.CHEM155_gr_34.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_35.gif]
[Graphics:Images/SOL_PS4.p9.CHEM155_gr_36.gif]

Therefore
delx  delp >= [Graphics:Images/SOL_PS4.p9.CHEM155_gr_37.gif]


Converted by Mathematica      October 24, 2002