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For a system of bosons at room temperature, compute the average occupancy of a single-particle state and the probability of the state containing 0,1,2,3bosons, if the energy of the state is

(a) 0.001eVgreater than μ

(b) 0.01eVgreater than μ

(c) 0.1eVgreater than μ

(d) 1eVgreater than μ

Short Answer

Expert verified

Result is:

The energuy state is: (a).n¯=25.2

The energuy state is: (b).localid="1651000533351" n¯=2.10

The energuy state is: (c).localid="1651000556743" n¯=0.0208

The energuy state is: (d).localid="1651000583464" n¯=1.244×10-17

Step by step solution

01

Part(a) Step 1:Given information

We have been given that n¯=1e(ϵ-μ)/kT-1

02

Part(a) Step 2: Simplify

Here

P(n)=e-n(ϵ-μ)/kT1-e-(ϵ-μ)/kT

kT=8.62×10-5eV/K(298K)=0.02569eV

to find the average occupancy:

n¯=1e0.001eV/0.02569eV-1

n¯=25.2

if it contains n=1

P(1)=e-(1)(0.001eV)/0.02569eV1-e-0.001eV/0.02569eV

P(1)=0.03672

if it contains n=3

P(3)=e-(3)(0.001eV)/0.02569eV1-e-0.001eV/0.02569eV

P(3)=0.034

03

Part(b) Step 1:Given information

We have been given that ϵ-μ=0.01eV

04

Part(b) Step 2: Simplify

If it contain n=0

P(0)=e-(0)(0.01eV)/0.02569eV1-e-0.01eV/0.02569eV

P(0)=0.322

If it contains n=1

P(1)=e-(1)(0.01eV)/0.02569eV1-e-0.01eV/0.02569eV

P(1)=0.218

05

Part(c) Step 1: Given information

We have been given that ϵ-μ=0.1eV

06

Part(c) Step 2: Simplify

If it contains n=0

P(0)=e-(0)(0.1eV)/0.02569eV1-e-0.1eV/0.02569eV

P(0)=0.9796

If it contains n=1

P(1)=e-(1)(0.1eV)/0.02569eV1-e-0.1eV/0.02569eV

P(1)=0.020

07

Part(d) Step 1:Given information

We have been given that ϵ-μ=1eV

08

Part(d) Step 2: Simplify

If it contains n=0

P(0)=e-(0)(1eV)/0.02569eV1-e-1eV/0.02569eV

P(0)=1

If it contains n=1

P(1)=e-(1)(1eV)/0.02569eV1-e-1eV/0.02569eV

P(1)=1.244×10-17

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Most popular questions from this chapter

Most spin-1/2 fermions, including electrons and helium-3 atoms, have nonzero magnetic moments. A gas of such particles is therefore paramagnetic. Consider, for example, a gas of free electrons, confined inside a three-dimensional box. The z component of the magnetic moment of each electron is ±µa. In the presence of a magnetic field B pointing in the z direction, each "up" state acquires an additional energy of -μBB, while each "down" state acquires an additional energy of +μBB

(a) Explain why you would expect the magnetization of a degenerate electron gas to be substantially less than that of the electronic paramagnets studied in Chapters 3 and 6, for a given number of particles at a given field strength.

(b) Write down a formula for the density of states of this system in the presence of a magnetic field B, and interpret your formula graphically.

(c) The magnetization of this system is μBN-N, where Nr and N1 are the numbers of electrons with up and down magnetic moments, respectively. Find a formula for the magnetization of this system at T=0, in terms of N, µa, B, and the Fermi energy.

(d) Find the first temperature-dependent correction to your answer to part (c), in the limit TTF. You may assume that μBBkT; this implies that the presence of the magnetic field has negligible effect on the chemical potential μ. (To avoid confusing µB with µ, I suggest using an abbreviation such as o for the quantity µaB.)

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(a) Imagine that the universe has some finite total volume V, but that V is increasing with time. Write down a formula for the total entropy of the electrons, positrons, and photons as a function of V and T, using the auxiliary functions u(T) and f(T) introduced in the previous problem. Argue that this total entropy would have ben conserved in the early universe, assuming that no other species of particles interacted with these.

(b) The entropy of the neutrino radiation would have been separately conserved during this time period, because the neutrinos were unable to interact with anything. Use this fact to show that the neutrino temperature Tv and the photon temperature T are related by

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as the universe expands and cools. Evaluate the constant by assuming that T=Tv when the temperatures are very high.

(c) Calculate the ratio T/Tv, in the limit of low temperature, to confirm that the present neutrino temperature should be 1.95 K.

(d) Use a computer to plot the ratio T/Tv, as a function of T, for kT/mc2ranging from 0 to 3.*

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