# 5: Wave and Quantum Mechanics and X-rays¶

## Example number 5.1, Page number 145¶

In :
#importing modules
import math
from __future__ import division

#Variable declaration
h = 6.63*10**-34;        #planck's constant(J)
c = 3*10**8;           #velocity of light(m/s)
lamda = 6328;          #wavelength of laser(angstrom)
ev = 6.24*10**18;         #conversion factor from J to eV

#Calculation
lamda = lamda*10**-10;        #wavelength of laser(m)
E = h*c/lamda;          #energy of photon(J)
Eev = E*ev;               #energy of photon(eV)
Eev = math.ceil(Eev*10**3)/10**3;   #rounding off to 3 decimals

#Result
print "energy of photon is",round(E/1e-19,2),"*10**-19 J or",Eev,"eV"

energy of photon is 3.14 *10**-19 J or 1.962 eV


## Example number 5.2, Page number 145¶

In :
#importing modules
import math
from __future__ import division

#Variable declaration
lamda = 6730;       #wavelength of laser(angstrom)
p = 1;           #output power(mW)
h = 6.63*10**-34;        #planck's constant(J)
c = 3*10**8;           #velocity of light(m/s)

#Calculation
p = p*10**-3;         #output power(W)
lamda = lamda*10**-10;        #wavelength of laser(m)
n = p*lamda/(h*c);         #number of photons(per sec)

#Result
print "number of photons emitted is",round(n/1e+15,2),"*10**15 per sec"
print "answer given in the book is wrong"

number of photons emitted is 3.38 *10**15 per sec
answer given in the book is wrong


## Example number 5.3, Page number 146¶

In :
#importing modules
import math
from __future__ import division

#Variable declaration
l = 3*10**-2;        #coherence length for sodium light(m)
lamda = 5893;      #wavelength(angstrom)
c = 3*10**8;           #velocity of light(m/s)

#Calculation
lamda = lamda*10**-10;        #wavelength(m)
n = l/lamda;       #number of oscillations
tc = l/c;          #coherence time(s)

#Result
print "number of oscillations is",round(n)
print "the coherence time is",tc,"s"

number of oscillations is 50908.0
the coherence time is 1e-10 s