# Chapter 18 :Quantum Physics¶

## Example 18.1 , Page no:108¶

In [1]:
import math
from __future__ import division

#initialisation of variables
f=5*10**14; #frequency in Hz (given)
h=6.63*10**-34; #planck's constant in J.sec

#CALCULATIONS
E=h*f; #calculating energy
E1=3*E;

#RESULTS
print"Total Energy in Joule =",'%.3E'%E1;

Total Energy in Joule = 9.945E-19


## Example 18.2 , Page no:108¶

In [2]:
import math
from __future__ import division

#initialisation of variables
c=3*10**8; #velocity in m/sec
l=5.5*10**-7; #wavelength in m
h=6.63*10**-34; #planck's constant in J.sec

#CALCULATIONS
f=c/l; #calculating frequency
E=h*f; #calculating energy
E1=100/E;

#RESULTS
print"Frequency in Hz =",'%.3E'%f;
print"Energy in Joule =",'%.3E'%E;
print"No. of photons emitted per second =",'%.3E'%E1;

Frequency in Hz = 5.455E+14
Energy in Joule = 3.616E-19
No. of photons emitted per second = 2.765E+20


## Example 18.3 , Page no:109¶

In [3]:
import math
from __future__ import division

#initialisation of variables
m=9.1*10**-31; #mass of electron in kg
v=10**7; #velocity in m/sec

#CALCULATIONS
KE=(1/2)*m*v*v; #calculating kinetic energy in Joule
KE1=KE/(1.6*10**-19);

#RESULTS
print"Kinetic energy in Joule =",'%.3E'%KE;
print"Kinetic energy in eV =",round(KE1,3);

Kinetic energy in Joule = 4.550E-17
Kinetic energy in eV = 284.375


## Example 18.4 , Page no:109¶

In [4]:
import math
from __future__ import division

#initialisation of variables
e=1.6*10**-19; #charge
ke=200; #kinetic energy in eV
m=1.67*10**-27; #mass in kg

#CALCULATIONS
KE=ke*e; #calculating kinetic energy
v=math.sqrt((2*KE)/m);  #calculating velocity

#RESULTS
print"Kinetic Energy in Joule =",'%.3E'%KE;
print"Velocity in m/sec =",round(v,3);

Kinetic Energy in Joule = 3.200E-17
Velocity in m/sec = 195763.514


## Example 18.5 , Page no:109¶

In [5]:
import math
from __future__ import division

#initialisation of variables
e=1.6*10**-19; #charge
c=3*10**8; #velocity in m/sec
ke=106*10**6; #kinetic energy in eV

#CALCULATIONS
KE=ke*e; #calculating kinetic energy
m=KE/(c*c); #Einstein's equation
m1=m/(9.1*10**-31);

#RESULTS
print"Kinetic Energy in Joule =",'%.3E'%KE;
print"Mass in kg =",'%.3E'%m;
print"Times electron mass =",round(m1,3);

Kinetic Energy in Joule = 1.696E-11
Mass in kg = 1.884E-28
Times electron mass = 207.082


## Example 18.6 , Page no:109¶

In [6]:
import math
from __future__ import division

#initialisation of variables
e=1.6*10**-19; #charge
c=3*10**8; #velocity in m/sec
KE=1.6*10**-19; #change in energy

#CALCULATIONS
m=KE/(c*c); #Einstein's equation
m1=m/(3*10**-26);

#RESULTS
print"Mass in kg =",'%.3E'%m;
print"Times mass of H20 molecule =",'%.3E'%m1;

Mass in kg = 1.778E-36
Times mass of H20 molecule = 5.926E-11


## Example 18.7 , Page no:109¶

In [7]:
import math
from __future__ import division

#initialisation of variables
c=3*10**8; #velocity in m/sec
l=5*10**-7; #wavelength in m
h=6.63*10**-34; #planck's constant in J.sec

#CALCULATIONS
f=c/l; #calculating frequency
E=h*f; #calculating energy
E1=E/(1.6*10**-19);

#RESULTS
print"Frequency in Hz =",'%.3E'%f;
print"Energy in Joule =",'%.3E'%E;
print"(a)Max. energy of photons that emerge =",round(E1,3);

Frequency in Hz = 6.000E+14
Energy in Joule = 3.978E-19
(a)Max. energy of photons that emerge = 2.486


## Example 18.8 , Page no:110¶

In [8]:
import math
from __future__ import division

#initialisation of variables
h=6.63*10**-34; #planck's constant in J.sec
e=1.6*10**-19; #in Coloumb
V=10**4; #potential difference in Volt

#CALCULATIONS
f=(e*V)/h; #calculating frequency

#RESULTS
print"Frequency in Hz =",'%.3E'%f;

Frequency in Hz = 2.413E+18


## Example 18.9 , Page no:110¶

In [9]:
import math
from __future__ import division

#initialisation of variables
c=3*10**8; #velocity in m/sec
l=2*10**-11; #wavelength in m
e=1.6*10**-19; #in Coloumb
h=6.63*10**-34; #planck's constant in J.sec

#CALCULATIONS
f=c/l; #calculating frequency
V=(h*f)/e; #calculating energy

#RESULTS
print"Frequency in Hz =",'%.3E'%f;
print"operating Voltage in Volt =",round(V,3);

Frequency in Hz = 1.500E+19
operating Voltage in Volt = 62156.25


## Example 18.10 , Page no:110¶

In [10]:
import math
from __future__ import division

#initialisation of variables
m=10**3; #mass in kg
v=20; #velocity in m/sec
h=6.63*10**-34; #planck's constant in J.sec

#CALCULATIONS
l=h/(m*v); #calculating energy

#RESULTS
print"Wavelength in m =",'%.3E'%l;

Wavelength in m = 3.315E-38


## Example 18.11 , Page no:111¶

In [11]:
import math
from __future__ import division

#initialisation of variables
e=1.6*10**-19; #charge
ke=1.5*10**4; #kinetic energy in eV
m=9.1*10**-31; #mass in kg
h=6.63*10**-34; #planck's constant in J.sec

#CALCULATIONS
KE=ke*e; #calculating kinetic energy
v=math.sqrt((2*KE)/m); #calculating velocity
l=h/(m*v); #calculating wavelength

#RESULTS
print"Kinetic Energy in Joule =",'%.3E'%KE;
print"Velocity in m/sec =",round(v,3);
print"Wavelength in metre =",'%.3E'%l;

Kinetic Energy in Joule = 2.400E-15
Velocity in m/sec = 72627303.92
Wavelength in metre = 1.003E-11


## Example 18.13 , Page no:111¶

In [12]:
import math
from __future__ import division

#initialisation of variables
h=6.63*10**-34; #planck's constant in J.sec
delx=10**-9; #in m
m=9.1*10**-31; #mass in kg

#CALCULATIONS
u=h/(2*3.14*delx); #uncertainty principle
delv=u/m; #uncertainty principle
u1=u*1,;

#RESULTS
print"Uncertainty in electrons momentum in kg.m/sec =",'%.3E'%u;
print"Uncertainty in electrons velocity in m/sec =",round(delv,2);
print"Uncertainty in electrons position in m =",'%.3E'%u1;

Uncertainty in electrons momentum in kg.m/sec = 1.056E-25
Uncertainty in electrons velocity in m/sec = 116014.56
Uncertainty in electrons position in m = 1.056E-25


## Example 18.14 , Page no:111¶

In [13]:
import math
from __future__ import division

#initialisation of variables
h=6.63*10**-34; #planck's constant in J.sec
delx=10**-10; #in m
m=9.1*10**-31; #mass in kg

#CALCULATIONS
u=h/(2*3.14*delx); #uncertainty principle
KE=(1/(2*m))*(u*u); #uncertainty principle

#RESULTS
print"Uncertainty in electrons momentum in kg.m/sec =",'%.3E'%u;
print"Uncertainty in electrons kinetic energy in Joule =",'%.3E'%KE;

Uncertainty in electrons momentum in kg.m/sec = 1.056E-24
Uncertainty in electrons kinetic energy in Joule = 6.124E-19