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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

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.

Change variables in equation 7.83 to λ=hc/ϵ and thus derive a formula for the photon spectrum as a function of wavelength. Plot this spectrum, and find a numerical formula for the wavelength where the spectrum peaks, in terms of hc/kT. Explain why the peak does not occur at hc/(2.82kT).

Show that when a system is in thermal and diffusive equilibrium with a reservoir, the average number of particles in the system is

N—=kTZ∂Z∂μ

where the partial derivative is taken at fixed temperature and volume. Show also that the mean square number of particles is

N2¯=(kT)2Z∂2Z∂μ2

Use these results to show that the standard deviation of Nis

σN=kT∂N—/∂μ,

in analogy with Problem6.18Finally, apply this formula to an ideal gas, to obtain a simple expression forσNin terms ofN¯Discuss your result briefly.

At the center of the sun, the temperature is approximately 107K and the concentration of electrons is approximately 1032 per cubic meter. Would it be (approximately) valid to treat these electrons as a "classical" ideal gas (using Boltzmann statistics), or as a degenerate Fermi gas (with T≈0 ), or neither?

Consider a two-dimensional solid, such as a stretched drumhead or a layer of mica or graphite. Find an expression (in terms of an integral) for the thermal energy of a square chunk of this material of area , and evaluate the result approximately for very low and very high temperatures. Also, find an expression for the heat capacity, and use a computer or a calculator to plot the heat capacity as a function of temperature. Assume that the material can only vibrate perpendicular to its own plane, i.e., that there is only one "polarization."

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