# 3: Inadequacy of Classical Physics¶

## Example number 1, Page number 128¶

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

#Variable declaration
me=9.1*10**-31;           #mass of electron(kg)
h=6.6*10**-34;            #planks constant(Js)
c=3*10**8;                #velocity(m/sec)
lamda=1700*10**-10;       #wavelength(m)
lamda0=2300*10**-10;      #wavelength(m)

#Calculations
KE=h*c*((1/lamda)-(1/lamda0));       #maximum energy of photoelectron(J)
vmax=math.sqrt(2*KE/me);             #maximum velocity of electron(ms-1)

#Result
print "maximum energy of photoelectron is",round(KE*10**19,3),"*10**-19 J"
print "maximum velocity of electron is",round(vmax/10**5,2),"*10**5 ms-1"
maximum energy of photoelectron is 3.038 *10**-19 J
maximum velocity of electron is 8.17 *10**5 ms-1

## Example number 2, Page number 128¶

In [9]:
#importing modules
import math
from __future__ import division

#Variable declaration
e=1.6*10**-19;            #charge(coulomb)
W=2.3*e;                  #work function(J)
h=6.6*10**-34;            #planks constant(Js)
c=3*10**8;                #velocity(m/sec)
lamda=6850;               #wavelength of orange light(angstrom)

#Calculations
lamda0=h*c/W;             #threshold wavelength(m)

#Result
print "threshold wavelength is",int(lamda0*10**10),"angstrom"
print "since wavelength of orange light is more, photoelectric effect doesn't take place"
threshold wavelength is 5380 angstrom
since wavelength of orange light is more, photoelectric effect doesn't take place

## Example number 3, Page number 129¶

In [11]:
#importing modules
import math
from __future__ import division

#Variable declaration
e=1.6*10**-19;            #charge(coulomb)
W=1.3*e;                  #work function(J)
h=6.6*10**-34;            #planks constant(Js)
new=6*10**14;             #frequency(Hertz)

#Calculations
V0=((h*new)-W)/e;         #retarding potential(volts)

#Result
print "retarding potential is",V0,"volts"
retarding potential is 1.175 volts

## Example number 4, Page number 129¶

In [15]:
#importing modules
import math
from __future__ import division

#Variable declaration
h=6.6*10**-34;            #planks constant(Js)
e=1.6*10**-19;            #charge(coulomb)
c=3*10**8;                #velocity(m/sec)
lamda=3*10**-7;           #wavelength(m)
me=9.1*10**-31;           #mass of electron(kg)
v=1*10**6;                #velocity(m/sec)

#Calculations
W=(h*c/lamda)-(me*v**2/2);      #work function(J)
W=W/e;                          #work function(eV)

#Result
print "work function is",round(W,2),"eV"
work function is 1.28 eV

## Example number 5, Page number 129¶

In [19]:
#importing modules
import math
from __future__ import division

#Variable declaration
h=6.6*10**-34;            #planks constant(Js)
e=1.6*10**-19;            #charge(coulomb)
c=3*10**8;                #velocity(m/sec)
lamda=4600*10**-10;       #wavelength(m)
qe=0.5;                   #efficiency(%)

#Calculations
E=h*c/lamda;              #energy(J)
n=10**-3/E;               #number of photons/second
i=n*qe*e*10**6/100;       #photoelectric current(micro ampere)

#Result
print "photoelectric current is",round(i,2),"micro ampere"
photoelectric current is 1.86 micro ampere

## Example number 6, Page number 130¶

In [23]:
#importing modules
import math
from __future__ import division

#Variable declaration
T1=3*10**-19;             #temperature(J)
T2=1*10**-19;             #temperature(J)
c=3*10**8;                #velocity(m/sec)
lamda1=3350;              #wavelength(m)
lamda2=5060;              #wavelength(m)

#Calculations
x=10**10*((1/lamda1)-(1/lamda2));
h=(T1-T2)/(c*x);          #planck's constant(joule second)

#Result
print "planck's constant is",round(h*10**34,2),"*10**-34 joule second"
planck's constant is 6.61 *10**-34 joule second

## Example number 7, Page number 131¶

In [36]:
#importing modules
import math
from __future__ import division

#Variable declaration
c=3*10**8;               #velocity of light(m/sec)
m0=9.1*10**-31;          #mass(kg)
h=6.62*10**-34;          #planks constant(Js)
lamda=3*10**-10;         #wavelength(angstrom)
lamda_dash=3.058;        #wavelength(angstrom)

#Calculations
lamda_sr=h/(m0*c);
E=h*c*((1/lamda)-(1/lamda_dash));                  #energy of recoil electron(joule)

#Result
print "wavelength of scattered radiation is",lamda_dash*10**10,"angstrom"
print "energy of recoil electron is",round(E*10**18,2),"*10**-18 joule"
print "answers given in the book are wrong"
wavelength of scattered radiation is 3.0121 angstrom
energy of recoil electron is 2.66 *10**-18 joule
answers given in the book are wrong

## Example number 8, Page number 132¶

In [42]:
#importing modules
import math
from __future__ import division

#Variable declaration
c=3*10**8;               #velocity of light(m/sec)
m0=9.1*10**-31;          #mass(kg)
h=6.62*10**-34;          #planks constant(Js)
lamda=2*10**-10;         #wavelength(angstrom)

#Calculations
lamda_sr=h/(m0*c);
E=h*c*((1/lamda)-(1/lamda_dash));                  #energy of recoil electron(joule)
x=1+(E/(m0*c**2));
v=c*math.sqrt(1-((1/x)**2));                       #velocity of recoil electron(m/sec)

#Result
print "wavelength of scattered radiation is",round(lamda_dash*10**10,3),"angstrom"
print "velocity of recoil electron is",round(v/10**8,4),"*10**8 ms-1"
print "answer for velocity given in the book is wrong"
wavelength of scattered radiation is 2.003 angstrom
velocity of recoil electron is 0.0188 *10**8 ms-1
answer for velocity given in the book is wrong

## Example number 9, Page number 133¶

In [49]:
#importing modules
import math
from __future__ import division

#Variable declaration
c=3*10**8;               #velocity of light(m/sec)
e=1.6*10**-19;           #charge(coulomb)
m0=9.1*10**-31;          #mass(kg)
h=6.62*10**-34;          #planks constant(Js)
lamda=3*10**-10;         #wavelength(m)

#Calculations
lamda_dash=lamda+(h*(1-math.cos(theta))/(m0*c));   #wavelength of scattered photon(m)
E=h*c*((1/lamda)-(1/lamda_dash));                  #energy of recoil electron(joule)
x=h/(lamda*m0*c);
tanphi=lamda*math.sin(theta)/(lamda_dash-(lamda*math.cos(theta)));
phi=phi*180/math.pi;                               #direction of recoil electron(degrees)
phim=60*(phi-int(phi));                            #angle(minutes)

#Result
print "wavelength of scattered photon is",round(lamda_dash*10**10,3),"angstrom"
print "energy of recoil electron is",round(E*10**17,1),"*10**-17 joules"
print "direction of recoil electron is",int(phi),"degrees",int(phim),"minutes"
print "answer for angle given in the book is wrong"
wavelength of scattered photon is 3.024 angstrom
energy of recoil electron is 0.5 *10**-17 joules
direction of recoil electron is 44 degrees 46 minutes
answer for angle given in the book is wrong

## Example number 10, Page number 134¶

In [51]:
#importing modules
import math
from __future__ import division

#Variable declaration
c=3*10**8;               #velocity of light(m/sec)
e=1.6*10**-19;           #charge(coulomb)
m0=9.1*10**-31;          #mass(kg)
h=6.62*10**-34;          #planks constant(Js)
E=1.96*10**6*e;          #energy of scattered photon(J)

#Calculations
lamda=h*c/E;             #wavelength(m)
delta_lamda=2*h/(m0*c);
lamda_dash=lamda+delta_lamda;   #wavelength of scattered photon(m)
Edash=h*c/(e*lamda_dash);       #energy of scattered photon(eV)

#Result
print "energy of scattered photon is",round(Edash/10**6,3),"MeV"
energy of scattered photon is 0.226 MeV

## Example number 11, Page number 135¶

In [65]:
#importing modules
import math
from __future__ import division

#Variable declaration
c=3*10**8;               #velocity of light(m/sec)
e=1.6*10**-19;           #charge(coulomb)
m0=9.1*10**-31;          #mass(kg)
h=6.6*10**-34;           #planks constant(Js)
E=500*10**3*e;           #energy of scattered photon(J)

#Calculations
lamda=h*c/E;             #wavelength(m)
delta_lamda=h*(1-math.cos(theta))/(m0*c);
E=h*c*((1/lamda)-(1/lamda_dash));       #energy of recoil electron(J)
tanphi=lamda*math.sin(theta)/(lamda_dash-(lamda*math.cos(theta)));