# 7: Classification of Solids¶

## Example number 7.1, Page number 138¶

In [2]:
#import modules
import math
from __future__ import division

#Variable declaration
W=11000;     #wavelength(angstrom)

#Calculation
Eg=W/12400;     #energy gap(eV)

#Result
print "Energy Gap is",round(Eg,3),"eV"

Energy Gap is 0.887 eV


## Example number 7.2, Page number 138¶

In [5]:
#import modules
import math
from __future__ import division

#Variable declaration
p=1.7*10**-6;      #resistivity(ohm-cm)
d=8.96;         #density(g/cc)
W=63.5;         #atomic weight(gm)
e=1.6*10**-19;     #the charge on electron(C)

#Calculation
n=8.96*Na/W;      #number of Cu atoms per cc
mewe=1/(p*e*n);     #mobility of electrons(cm^2/V-s)

#Result
print "mobility of electrons is",round(mewe,1),"cm^2/V-s"

mobility of electrons is 43.3 cm^2/V-s


## Example number 7.3, Page number 139¶

In [10]:
#import modules
import math
from __future__ import division

#Variable declaration
d1=2.5*10**19;      #density of charge carriers(per m^3)
d2=4.2*10**28;      #density of germanium atoms(per m^3)
mewe=0.36;          #mobilty of electrons(m^2/V-s)
Na=6.02*10**23;     #Avgraodo no.(per g-mol)
e=1.6*10**-19;      #the charge on electron(C)

#Calculation
Nd=d2/10**6;       #density of added impurity atoms(atoms/m^3)
sigma_n=Nd*e*mewe;        #conductivity(mho/m)
rho_n=1/sigma_n;          #resistivity of doped germanium(ohm-m)

#Result
print "resistivity of doped germanium is",round(rho_n*10**3,3),"*10**-3 ohm-m"

resistivity of doped germanium is 0.413 *10**-3 ohm-m


## Example number 7.4, Page number 139¶

In [12]:
#import modules
import math
from __future__ import division

#Variable declaration
Eg=0.75;      #energy gap(eV)

#Calculation
lamda=12400/Eg;     #wavelength(angstrom)

#Result
print "wavelength is",int(lamda),"angstrom"

wavelength is 16533 angstrom