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An experiment finds electrons to be uniformly distributed over the interval 0 cm x 2 cm, with no electrons falling out-side this interval.

a. Draw a graph of 0 c1x2 0 2 for these electrons.

b. What is the probability that an electron will land within the interval 0.79 to 0.81 cm?

c. If 106 electrons are detected, how many will be detected in the interval 0.79 to 0.81 cm?

d. What is the probability density at x = 0.80 cm?

Short Answer

Expert verified

The expression for the probability that a particle is found in a narrow intervalδxat position x is

Step by step solution

01

prob in δx at x=ψx2δx

Here,

ψx2is the probability density

According to the problem, the electrons are uniformly distributed over an interval of 0cm≤x≤2cm. so the probability ψx2is constant over the interval 0cm≤x≤2cmand thus ψx2is a square wave function

The condition for normalization is

ψx2=1

Determine the probability of an electron to be found over the interval 0cm≤x≤2cm

ψx2δx=1

Substitute 2cm for δx

ψx2δx=1

ψx2=0.5cm-1

02

(b)The narrow interval in which the electron is found is,δx=0.81cm-0.79cm    =0.02 cmDetermine the probability of an electron to be found over the interval 0.79cm to 0.81cmprobinδx at x=0.80 cm=ψx=0.80cm2δxSubstitute 0.02 cm for δx and 0.5cm-1 for ψx=0.80 cm2δxprobinδ x at x=0.80 cm=ψx=0.80cm2δx                                =0.50cm-10.02cm                                =0.01                                =1%

Thus the probability of an electron to be found over the interval 0.79 cm to 0.81cm is 1%

03

(c)The expression for number of electrons N landing in a narrow strip at position x is,

Ninδxatx=Nxprobinδxatx

Calculate the number of electrons detected in the interval 0.79cm to 0.81 cm

Ninδxatx=0.80cm=NxProbinδxatx=0.80cm

Thus the number of electrons detected in the interval 0.79cm to 0.81cm is 104

04

(d)Calculate the probability density at x=0.80 cm

probx=0.80cm=ψ=0.80cm2Probx=0.80cm=0.5cm-1

Thus the probability density at x-0.80 cm is 0.5 cm-1

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