# Chapter 7: Lasers and Holography¶

## Example 7.1, Page 410¶

In [2]:
#Variable declaration
e = 1.6e-019;  # Charge on an electron, eV
h = 6.62e-034;  # Planck's constant, J-s
c = 3e+008;  # Speed of light in vacuum, m/s
n = 2.8e+019;  # Number of photons in laser pulse
lamda = 7e-007;  # Wavelength of the radiation emited by the laser, m

#Calculations
E = (h*c)/(lamda*e);  # Energy of the photon in the laser light, eV
del_E = E*n;  # The energy of laser pulse having n photons, eV

#Result
print "The energy of the laser pulse = %4.2e eV"%del_E

The energy of the laser pulse = 4.97e+19 eV


## Example 7.2, Page 411¶

In [22]:
from math import *

#Variable declaration
c = 3.0e8;        #velocity of light, m/s
tc = 0.5e-9     #time duration of pulses(s)
lamda = 6.5e-7  #wavelength, m

#Calculations&Results
Lc = c*tc;    # coherence length, m
print "The coherence length is %.2f m"%Lc
del_v = 1/tc
print "Resultant bandwidth = %.e Hz"%del_v
del_lamda = (lamda**2*del_v)/c
print "Line width = %.2e m"%(del_lamda)

The coherence length is 0.15 m
Resultant bandwidth = 2e+09 Hz
Line width = 2.82e-12 m


## Example 7.3, Page 411¶

In [24]:
from math import *

#Variable declaration
a = 4e-003;  # Coherence width of laser source, m
lamda = 6e-007;  # Wavelength of the pulse, m
D = 100;  # Distance of the surface from laser source, m

#Calculations&Results

The angular spread = 3e-04 radian