# Chapter17-The Band Theory of Solids¶

## Ex1-pg522¶

In [1]:
import math
##Example 17.1
##calculation of probability

##given values
E=.01;##energy difference in eV
kT=.026;##temperture equivalent at room temp in e

##calculation
P=1/(1+(math.e**(E/kT)));

print'%s %.2f %s'%('interatomic spacing  is',P,'');

interatomic spacing  is 0.41


## Ex2-pg523¶

In [2]:
import math
##Example 17.2
##calculation of velocity of e

##given values
e=1.6*10**-19.;##charge of e in C
E=2.1*e;##fermi level in J
m=9.1*10**-31.;##mass of e in kg

##calculation
v=math.sqrt(2.*E/m);

print'%s %.2f %s'%('velocity of e(in m/s)',v,'');

velocity of e(in m/s) 859337.85


## Ex3-pg523¶

In [3]:
import math
##Example 17.3
##calculation of velocity of fraction of free electrons

##given values
E=5.5;##fermi level in eV
kT=.026;##temperture equivalent at room temp in e

##calculation
f=2.*kT/E;

print'%s %.4f %s'%('fraction of free electrone\s upto width kT on either side of Ef is',f,'');

fraction of free electrone\s upto width kT on either side of Ef is 0.0095