Verify that the probabilities shown in Table 9.1 for four distinguishable oscillators sharing energy 2δEagree with the exact probabilities given by equation (9-9).

Short Answer

Expert verified

The probabilities agree with the result from equation 1.

P(n)=(Mn+N2)!(Mn)!(N2)!/(M+N1)!M!(N1)!

Step by step solution

01

Concept of probability of finding a particle at an energy state

Probability of finding a particle at an energy state is:

P(n)=(Mn+N2)!(Mn)!(N2)!/(M+N1)!M!(N1)! ……. (1)

whereM, is the sum of nonnegative distinct quantum numbersniandNis the total number of particles.

02

Calculate the probability using equation (1)

Here, M=2,N=4, and the allowed values of nare n=0,1,2. Let us first consider n=0.

The probability is:

role="math" localid="1660022722768" P(n=0)=(20+42)!(20)!(42)!/(2+41)!2!(41)!=4!2!2!/5!2!3!=6/10=0.6

Forn=1, we get:

P(n=1)=(21+42)!(21)!(42)!/(2+41)!2!(41)!=3!1!2!/5!2!3!=3/10=0.3

Finally, for n=2, we get:

P(n=2)=(22+42)!(22)!(42)!/(2+41)!2!(41)!=2!0!2!/5!2!3!=1/10=0.1

We have thus verified that the probabilities agree with the result from equation 1.

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Most popular questions from this chapter

Example 9.2 obtains a ratio of the number of particles expected in the n = 2state lo that in the ground state. Rather than the n = 2state, consider arbitrary n.

(a) Show that the ratio is numberofenergyEnnumberofenergyE1=n2e-13.6cV(1-n-2)/kBT

Note that hydrogen atom energies are En=-13.6eV/st2.

(b) What is the limit of this ratio as n becomes very large? Can it exceed 1? If so, under what condition(s)?

(c) In Example 9.2. we found that even at the temperature of the Sun's surface(~6000K), the ratio for n = 2 is only 10-8 . For what value of nwould the ratio be 0.01?

(d) Is it realistic that the number of atoms with high n could be greater than the number with low n ?

Consider a simple thermodynamic system in which particles can occupy only two states: a lower state, whose energy we define as 0 , and an upper state, energyEu

(a) Cany out the sum (with only two states, integration is certainly not valid) giving the average particle energy E. and plot your result as a function of temperature.

(b) Explain qualitatively why it should behave as it does,

(c) This system can be used as a model of paramagnetic, where individual atoms' magnetic moments can either be aligned or anti aligned with an external magnetic field, giving a low or high energy, respectively. Describe how the average alignment or antialignment depends on temperature. Does it make sense'?

Show that equation (9- 16) follows from (9-15) and (9- 10).

In a large system of distinguishable harmonic oscillators, how high does the temperature have to be for the probability of occupying the ground state to be less than12?

What is special about a metastable Stale, and why is it so useful ina laser? Why wouldn't a non-metastable state at the same energy work?

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