# Chapter 21 :Theory of The Atom¶

## Example 21.5 , Page no:126¶

In :
import math
from __future__ import division

#initialisation of variables
e1=-13.6; #in eV

#CALCULATIONS
a=(e1/4);
b=(e1/9);
c=(e1/16);

#RESULTS
print"Energy of first excited state in eV =",round(a,3);
print"Energy of second excited state in eV =",round(b,3);
print"Energy of third excited state in eV =",round(c,3);

Energy of first excited state in eV = -3.4
Energy of second excited state in eV = -1.511
Energy of third excited state in eV = -0.85


## Example 21.6 , Page no:127¶

In :
import math
from __future__ import division

#initialisation of variables
h=6.63*10**-34; #Plancks constant in J.sec
m=9.1*10**-31; #mass in kg
r1=5.3*10**-11; #radius in m

#CALCULATIONS
v=h/(2*3.14*m*r1); #calculating velocity in m/sec

#RESULTS
print"Velocity in m/sec =",round(v,3);

Velocity in m/sec = 2188953.938


## Example 21.7 , Page no:127¶

In :
import math
from __future__ import division

#initialisation of variables
E=2.18*10**-18; #energy in Joule
k=1.38*10**-23; #constant in J/K

#CALCULATIONS
a=((2*E)/(3*k));

#RESULTS
print"Temperature in Kelvin =",round(a,3);

Temperature in Kelvin = 105314.01


## Example 21.8 , Page no:127¶

In :
import math
from __future__ import division

#initialisation of variables
E=2.18*10**-18; #energy in Joule
k=1.38*10**-23; #constant in J/K

#CALCULATIONS
a=E/h;

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

Frequency in Hz = 3.288E+15


## Example 21.11 , Page no:127¶

In :
import math
from __future__ import division

#initialisation of variables
e1=-13.6; #energy in eV

#CALCULATIONS
e=e1/9;

#RESULTS
print"Energy in eV =",round(e,3);

Energy in eV = -1.511