Chapter 5: Q31P (page 245)
Derive the Stefan-Boltzmann formula for the total energy density in blackbody radiation
Short Answer
Deriving the Stefan-Boltzmann formula for the total energy density in the blackbody radiation is
Chapter 5: Q31P (page 245)
Derive the Stefan-Boltzmann formula for the total energy density in blackbody radiation
Deriving the Stefan-Boltzmann formula for the total energy density in the blackbody radiation is
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Get started for freeDiscuss (qualitatively) the energy level scheme for helium if (a) electrons were identical bosons, and (b) if electrons were distinguishable particles (but with the same mass and charge). Pretend these “electrons” still have spin 1/2, so the spin configurations are the singlet and the triplet.
Find the average energy per free electron , as a fraction of the
Fermi energy. Answer:
Use the method of Lagrange multipliers to find the rectangle of largest area, with sides parallel to the axes that can be inscribed in the ellipse. What is the maximum area?
We can extend the theory of a free electron gas (Section 5.3.1) to the relativistic domain by replacing the classical kinetic energy, ,with the relativistic formula, . Momentum is related to the wave vector in the usual way: . In particular, in the extreme relativistic limit,
(a) Replace n Equation 5.55 by the ultra-relativistic expression, , and calculatein this regime.
(5.55).
(b) Repeat parts (a) and (b) of Problem 5.35 for the ultra-relativistic electron gas. Notice that in this case there is no stable minimum, regardless of R; if the total energy is positive, degeneracy forces exceed gravitational forces, and the star will expand, whereas if the total is negative, gravitational forces win out, and the star will collapse. Find the critical number of nucleons, Nc , such that gravitational collapse occurs for is called the Chandrasekhar limit.
(c) At extremely high density, inverse beta decay,converts virtually all of the protons and electrons into neutrons (liberating neutrinos, which carry off energy, in the process). Eventually neutron degeneracy pressure stabilizes the collapse, just as electron degeneracy does for the white dwarf (see Problem 5.35). Calculate the radius of a neutron star with the mass of the sun. Also calculate the (neutron) Fermi energy, and compare it to the rest energy of a neutron. Is it reasonable to treat a neutron star non relativistic ally?
Suppose you have three particles, and three distinct one-particle stateare available. How many different three-particle states can be constructed (a) if they are distinguishable particles, (b) if they are identical bosons, (c) if they are identical fermions? (The particles need not be in different states would be one possibility, if the particles are distinguishable.)
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