Question 4: (a) What is heat capacity? Explain the Dulong-Petit rule for the heat capacity of the solids? (b) Why do we need Debye model to explain heat capacity of solids? (c) Which one has a higher Debye temperature, lead or diamond? Why? (d) Estimate the value of the force constant (Y) and angular frequency o for the vibrations of the atoms in copper. Y= 130 GPa and cubic lattice constant a=0.36 nm. Then estimate the angular frequency o for the vibrations that correspond to Debye temperature of 343 K and compare these two angular frequencies. Planck constant 6.6260755 x 10-s 4.13566743 x 10-15 eV's Boltzmann constant kg 1.380658 x 10-23 K-1 Mass of copper: 63.546 u and lamu= 1.67x10-27 kg