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The speed of sound in copper is 3560m/s. Use this value to calculate its theoretical Debye temperature. Then determine the experimental Debye temperature from Figure 7.28, and compare.

Short Answer

Expert verified

Hence, the Debye Temperature from experimental Data (graph) TD=359.9176K.

Step by step solution

01

Step 1. Given information

We have,the speed of sound in copper is3560m/s

The Debye temperature isTD=hCs2kB6NV13.


02

Step 2. Putting the value of h , V , N ,CS ,kB.

V=7.11cm3/mol

Cs=3560m/s=3560100cm/s

N=6.0221023atoms/mol

kB=1.38110-23J/K

h=6.62610-34Js

substituting all the above value in Debye Temperature we get

TD=6.62610-34Js3560100cm/s21.38110-23J/K66.0221023/mol7.11cm3/mol13

TD=465.3381K

03

Step 3.  Calculating the experimental Debye Temperature.

Take any two points on experimental data calculate the slope [Approximately] Approximately take two points

Approximately take two points

A(0,0.75)B(18,1.5)

CVTT2=1.5-0.7518-0

=0.0417

04

Step 4. Finding the slope of the graph.

Slope:CVTT2=124NkB5TD3

124NkB5TD3=0.0417mJ/K4

then , the Debye Temperature

TD=124NkB50.041710-3J/K413

=1246.02210231.38110-2350.041710-313

=359.9176K

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Most popular questions from this chapter

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" kTF路 Also show that the heat capacity has the expected behavior when kTF. Sketch the heat capacity as a function of temperature.

Consider a gas of noninteracting spin-0 bosons at high temperatures, when TTc. (Note that 鈥渉igh鈥 in this sense can still mean below 1 K.)

  1. Show that, in this limit, the Bose-Einstein function can be written approximately as
    nBE=e()/kT[1+e/kT+].
  2. Keeping only the terms shown above, plug this result into equation 7.122 to derive the first quantum correction to the chemical potential for gas of bosons.
  3. Use the properties of the grand free energy (Problems 5.23 and 7.7) to show that the pressure of any system is given by In P=(kT/V), where Zis the grand partition function. Argue that, for gas of noninteracting particles, In Zcan be computed as the sum over all modes (or single-particle states) of In Zi, where Zi; is the grand partition function for the ithmode.
  4. Continuing with the result of part (c), write the sum over modes as an integral over energy, using the density of states. Evaluate this integral explicitly for gas of noninteracting bosons in the high-temperature limit, using the result of part (b) for the chemical potential and expanding the logarithm as appropriate. When the smoke clears, you should find
    p=NkTV(1NvQ42V),
    again neglecting higher-order terms. Thus, quantum statistics results in a lowering of the pressure of a boson gas, as one might expect.
  5. Write the result of part (d) in the form of the virial expansion introduced in Problem 1.17, and read off the second virial coefficient, B(T). Plot the predicted B(T)for a hypothetical gas of noninteracting helium-4 atoms.
  6. Repeat this entire problem for gas of spin-1/2 fermions. (Very few modifications are necessary.) Discuss the results, and plot the predicted virial coefficient for a hypothetical gas of noninteracting helium-3 atoms.

(a) Estimate (roughly) the total power radiated by your body, neglecting any energy that is returned by your clothes and environment. (Whatever the color of your skin, its emissivity at infrared wavelengths is quite close to 1; almost any nonmetal is a near-perfect blackbody at these wavelengths.)

(b) Compare the total energy radiated by your body in one day (expressed in kilocalories) to the energy in the food you cat. Why is there such a large discrepancy?

(c) The sun has a mass of 21030kgand radiates energy at a rate of 3.91026watts. Which puts out more power per units mass-the sun or your body?

The Sommerfeld expansion is an expansion in powers of kTF, which is assumed to be small. In this section I kept all terms through order kTF2, omitting higher-order terms. Show at each relevant step that the term proportional to localid="1650117451748" T3is zero, so that the next nonvanishing terms in the expansions forlocalid="1650117470867" and localid="1650117476821" Uare proportional to localid="1650117458596" T4. (If you enjoy such things, you might try evaluating the localid="1650117464980" T4terms, possibly with the aid of a computer algebra program.)

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 =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 calculated 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.

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