#importing modules
import math
from __future__ import division
#Variable declaration
k=1.38*10**-23; #boltzmann constant(J/K)
T=1000; #temperature(K)
new1=7.5*10**14;
new2=4.3*10**14;
h=6.626*10**-34; #planck's constant(Js)
#Calculation
kT=k*T;
#optical region extends from 4000 to 7000 angstrom
hnew=h*(new1-new2);
#Result
print "value of kT is",kT,"J"
print "value of hnew is",hnew,"J"
print "hnew>kT.therefore spontaneous transitions are dominant ones in optical region"
#importing modules
import math
from __future__ import division
#Variable declaration
h=6.626*10**-34; #planck's constant(Js)
c=3*10**8; #velocity of light(m/sec)
P=0.6; #power(watt)
T=30*10**-3; #time(s)
lamda=640*10**-9; #wavelength(m)
#Calculation
E=P*T; #energy deposited(J)
n=E*lamda/(h*c); #number of photons in each pulse
#Result
print "energy deposited is",E,"J"
print "number of photons in each pulse is",round(n/10**16,1),"*10**16"
#importing modules
import math
from __future__ import division
#Variable declaration
lamda=5000*10**-10; #wavelength(m)
f=0.2; #focal length(m)
a=0.009; #radius of aperture(m)
P=2.5*10**-3; #power(W)
#Calculation
A=math.pi*lamda**2*f**2/a**2; #area of spot at focal plane(m**2)
I=P/A; #intensity at focus(W/m**2)
#Result
print "area of spot at focal plane is",round(A*10**10,2),"*10**-10 m**2"
print "intensity at focus is",round(I/10**6,3),"*10**6 W/m**2"
#importing modules
import math
from __future__ import division
#Variable declaration
lamda=693*10**-9; #wavelength(m)
D=3*10**-3; #diameter of mirror(m)
d=300*10**3; #distance from earth(m)
#Calculation
delta_theta=1.22*lamda/D; #angular spread(rad)
a=delta_theta*d; #diameter of beam on satellite(m)
#Result
print "angular spread is",round(delta_theta*10**4,2),"*10**-4 rad"
print "diameter of beam on satellite is",round(a,2),"m"