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please answer c) only
2. a) A spinless particle, mass m, is confined to a two-dimensional box of length L. The stationary
Schrödinger equation is -
+a) v(x, y) = Ev(x, y), for 0 < r, y < L. The bound-
ary conditions on ý are that it vanishes at the edges of the box. Verify that solutions are given
by
2
v(1, y)
sin
L
where n., ny = 1,2..., and find the corresponding energy.
Let L and m be such that h'n?/(2mL²) = 1 eV. How many states of the system have energies
between 9 eV and 24 eV?
b) We now consider a macroscopic box (L of order cm) so that h'n?/(2mL?) ~ 10-20 eV. If we
define the wave vector k as ("", ""), show that the density of states g(k), defined such that
the number of states with |k| between k and k +dk is given by g(k)dk, is
Ak
9(k) =
27
c) Use the expression for g(k) to show that at room temperature the partition function for the
translational energy of a particle in a macroscopic 2-dimensional box is Z1 = Aoq, where
2/3
oq = ng = mk„T/2nh?. Hence show that the average energy of the particle is kT, and
explain the result.
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Transcribed Image Text:please answer c) only 2. a) A spinless particle, mass m, is confined to a two-dimensional box of length L. The stationary Schrödinger equation is - +a) v(x, y) = Ev(x, y), for 0 < r, y < L. The bound- ary conditions on ý are that it vanishes at the edges of the box. Verify that solutions are given by 2 v(1, y) sin L where n., ny = 1,2..., and find the corresponding energy. Let L and m be such that h'n?/(2mL²) = 1 eV. How many states of the system have energies between 9 eV and 24 eV? b) We now consider a macroscopic box (L of order cm) so that h'n?/(2mL?) ~ 10-20 eV. If we define the wave vector k as ("", ""), show that the density of states g(k), defined such that the number of states with |k| between k and k +dk is given by g(k)dk, is Ak 9(k) = 27 c) Use the expression for g(k) to show that at room temperature the partition function for the translational energy of a particle in a macroscopic 2-dimensional box is Z1 = Aoq, where 2/3 oq = ng = mk„T/2nh?. Hence show that the average energy of the particle is kT, and explain the result.
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