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
```

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)
```

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
A = 2*lamda/a; # Angular spread of laser beam, radian
print "The angular spread = %1.0e radian"%A
theta = A/2; # Semi angle, radian
A_s = pi*(D*theta)**2; # Areal spread of laser beam, Sq.m
print "The areal spread = %1.0e Sq.m"%A_s
```