55.
(a) The average kinetic energy is
K =
3
2
kT =
3
2
(1.38
× 10
−23
J/K)(300 K) = 6.21
× 10
−21
J = 3.88
× 10
−2
eV .
(b) The de Broglie wavelength is
λ
=
h
√
2m
n
K
=
6.63
× 10
−34
J
·s
2(1.675
× 10
−27
kg)(6.21
× 10
−21
J)
=
1.5
× 10
−10
m .