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Suppose you have a "box" in which each particle may occupy any of 10single-particle states. For simplicity, assume that each of these states has energy zero.

(a) What is the partition function of this system if the box contains only one particle?

(b) What is the partition function of this system if the box contains two distinguishable particles?

(c) What is the partition function if the box contains two identical bosons?

(d) What is the partition function if the box contains two identical fermions?

(e) What would be the partition function of this system according to equation 7.16?

(f) What is the probability of finding both particles in the same single particle state, for the three cases of distinguishable particles, identical bosom, and identical fermions?

Short Answer

Expert verified

(a) Partition function of system with box having only one particle is 10.

(b) Partition function of the system if the box contains two distinguishable particles is 100.

(c) Partition function if the box contains two identical bosons is 55.

(d) Partition function if the box contains two identical fermions is 45.

(e) Partition function of this system according to equation 7.16 is 50.

(f) Probability of finding both particles in the same single particle state, for the three cases of distinguishable particles, identical bosom, and identical fermions are10%,18%and0%.

Step by step solution

01

Step 1. Calculation one particle

Each particle can have any 10states each with zero energy.

So, E(ri)=0for1≤ri≤10

Formula for particle function with box having one particle:

Zl=∑ie-βE(ri)

where, β=1kTβ=1kT

We substitute E(ri)=0

localid="1647243851142" Zl=∑110eβ(0)=∑1101=10

So, Partition function of system with box having only one particle is10.

02

Step 2. Calculation two particles

For two distinguishable particles partition function is:

Z=Zl2

Substitute Zl=10

role="math" localid="1647244178631" Z=(10)2=100

So, the partition function of the system if the box contains two distinguishable particles is100.

03

Step 3. Calculation bosons

To put two identical bosons in same single particle state the possibility is 10.

So, to put two identical bosons in different single particle state the possibility is calculated as:

C210=10!2!8!=45

So, total possible states are:

Z=10+45=55

Hence, the partition function if the box contains two identical bosons is55.

04

Step 4. Calculation fermions

There is no possibility to put two identical fermions in same single particle state.

For different single particle state possibilities are calculated by:

C210=10!2!8!=45

So, the partition function if the box contains two identical fermions is45.

05

Step 5. Calculation indistinguishable particles 

Partition function for Nindistinguishable and non interacting particles is given by,

Z=ZlNN!

Substitute Zl=10and N=2

Z=1022!=50

So, the partition function of the system when box have indistinguishable particles is50.

06

Step 6. Calculation probability

For distinguishable particles number of accessible states are Z=100.

For both particles in same single particle state, accessible states are 10.

So, probability of finding both particle in same single particle state is:

P=10100=10%

So, probability for distinguishable particles is role="math" localid="1647245922911" 10%.

For identical bosons number of accessible states are Z=55.

For both bosons in same single particle state, accessible states are 10.

So, probability of finding both bosons in same single particle state is:

P=1055=18%

So, probability for identical bosons is 18%.

For identical fermions number of accessible states are Z=45.

For both fermions in same single particle state, accessible states is 0.

So, probability of finding both fermions in same single particle state is:

P=045=0%

So, probability for identical fermions is 0%.

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Most popular questions from this chapter

The tungsten filament of an incandescent light bulb has a temperature of approximately 3000K. The emissivity of tungsten is approximately 13, and you may assume that it is independent of wavelength.

(a) If the bulb gives off a total of 100watts, what is the surface area of its filament in square millimetres?

(b) At what value of the photon energy does the peak in the bulb's spectrum occur? What is the wavelength corresponding to this photon energy?

(c) Sketch (or use a computer to plot) the spectrum of light given off by the filament. Indicate the region on the graph that corresponds to visible wavelengths, between400and700nm.

(d) Calculate the fraction of the bulb's energy that comes out as visible light. (Do the integral numerically on a calculator or computer.) Check your result qualitatively from the graph of part (c).

( e) To increase the efficiency of an incandescent bulb, would you want to raise or lower the temperature? (Some incandescent bulbs do attain slightly higher efficiency by using a different temperature.)

(f) Estimate the maximum possible efficiency (i.e., fraction of energy in the visible spectrum) of an incandescent bulb, and the corresponding filament temperature. Neglect the fact that tungsten melts at 3695K.

Figure 7.37 shows the heat capacity of a Bose gas as a function of temperature. In this problem you will calculate the shape of this unusual graph.

(a) Write down an expression for the total energy of a gas of Nbosons confined to a volume V, in terms of an integral (analogous to equation 7.122).

(b) For T<Tcyou can set μ=0. Evaluate the integral numerically in this case, then differentiate the result with respect to Tto obtain the heat capacity. Compare to Figure 7.37.

(c) Explain why the heat capacity must approach 32Nkin the high- Tlimit.

(d) For T>Tcyou can evaluate the integral using the values of μcalculated in Problem 7.69. Do this to obtain the energy as a function of temperature, then numerically differentiate the result to obtain the heat capacity. Plot the heat capacity, and check that your graph agrees with Figure 7.37.

Figure 7.37. Heat capacity of an ideal Bose gas in a three-dimensional box.

In Problem 7.28you found the density of states and the chemical potential for a two-dimensional Fermi gas. Calculate the heat capacity of this gas in the limit role="math" localid="1650099524353" kT≪εF· Also show that the heat capacity has the expected behavior when kT≫εF. Sketch the heat capacity as a function of temperature.

For a system of particles at room temperature, how large must ϵ-μbe before the Fermi-Dirac, Bose-Einstein, and Boltzmann distributions agree within 1%? Is this condition ever violated for the gases in our atmosphere? Explain.

Consider a system consisting of a single impurity atom/ion in a semiconductor. Suppose that the impurity atom has one "extra" electron compared to the neighboring atoms, as would a phosphorus atom occupying a lattice site in a silicon crystal. The extra electron is then easily removed, leaving behind a positively charged ion. The ionized electron is called a conduction electron, because it is free to move through the material; the impurity atom is called a donor, because it can "donate" a conduction electron. This system is analogous to the hydrogen atom considered in the previous two problems except that the ionization energy is much less, mainly due to the screening of the ionic charge by the dielectric behavior of the medium.

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