If the velocity of sound in a solid is of the order 103 m/s, compare the frequency of the sound wave λ = 20 Å for (a) a monoatomic system and (b) acoustic waves and optical waves in a diatomic system containing two identical atoms (M=m) per unit cell of interatomic spacing 2.2 Å.
4.1 The conductivity of silver is 6.5 x107 per Ohm per m and number of conduction electrons per m3 is 6x1028 Find the mobility of conduction electrons and the drift velocity in an electric field of 1 V/m. Given m = 9.1 x 10-31kg and e=1.602 x 10-19C.
4.2 What is Lorentz number? The thermal and electrical conductivities of Cu at 20oC are 390 Wm-1K-1 and 5.87x107W-1m-1 respectively. Calculate Lorentz number.