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Q13P

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Fundamentals Of Physics
Found in: Page 1215

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Short Answer

one-dimensional infinite well of length 200 pm contains an electron in its third excited state. We position an electron detector probe of width 2.00 pm so that it is centred on a point of maximum probability density. (a) What is the probability of detection by the probe? (b) If we insert the probe as described 1000 times, how many times should we expect the electron to materialize on the end of the probe (and thus be detected)?

(a) The probability of detection is 0.020.

(b) 20 times should we expect the electron to materialize on the end of

the probe.

See the step by step solution

Step by Step Solution

Step 1: Introduction

As the gas decays and gives off electrons, the detector uses a magnet to trap them in a magnetic bottle. A radio antenna then picks up very weak signals emitted by the electrons, which can be used to map the electrons' precise activity over several milliseconds.

Step 2: Concept

Probability of defection in width centred on position is given by

p(x)=ψn2(x)dx

Probability density ψxn2 for the trapped electron is

ψn2(x)=A2sin2 nπLx,[for n=1,2,3,...]

Step: 3 (a) Determine the probability of detection by the probe

Centred of the well, x=L2

=200 pm2=100 pm

Probability of detection at x ,

px=ψn2xdx =2LsinnπLx2dx =2Lsin2nπLxdx

Here,

n=3

Length, L=200 pm

Width of the probe, dx=2.00 pm

Probability

px=L2=2Lsin2Lxdx=2Lsin23πLL2dx=2Lsin23π2dx=2Ldx=2200 pm2.00 pm=0.020

Hence, the probability of detection is 0.020.

Step 4: (b) Determine the electron to materialize on the end of the probe

Number of independent insertion,

N=1000

Number of times the electron to be detected, n=Np

=10000.020=20

Hence, 20 times should we expect the electron to materialize on the end of

the probe.

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