Chapter 17, Electromagnetic waves

Example 1, page 550

In [2]:
from __future__ import division
from numpy import pi
# magnitude
#given data :
R=7*10**8 # in m
P=3.8*10**26 # in Watt
S=P/(4*pi*R**2) 
print "Magnitude of poynting vector, S = %0.3e W/m^2 " %S

Magnitude of poynting vector, S = 6.171e+07 W/m^2

Example 2, page 551

In [5]:
from numpy import pi
# Poynting vector
#given data :
R=1.5*10**11 # in m
P=3.8*10**26 # in Watt
S=P/(4*pi*R**2) # in W/m**2
Se=round(S*60/(4.2*10**4)) 
print "Poynting vector, Se = %0.2f cal/cm^2-m " %Se

Poynting vector, Se = 2.00 cal/cm^2-m

Example 3, page 560

In [8]:
from numpy import sqrt
# Amplitude and magnetic field
#given data :
S=2 # in cal/cm**2- min
EH=S*4.2*10**4/60 # joule/m**2 sec
mu0=4*pi*10**-7 
epsilon0=8.85*10**-12 
EbyH=sqrt(mu0/epsilon0) 
E=sqrt(EH*EbyH) 
H=EH/E 
E0=E*sqrt(2) 
H0=H*sqrt(2) 
print "E = %0.2f V/m "%E
print "H  = %0.3f Amp-turn/m "%H
print "Amplitude of electric fields of radiation, E0 = %0.f V/m  " %E0
print "Magnetice field of radition, H0 = %0.2f Amp-turn/m " %H0

E = 726.32 V/m 
H  = 1.928 Amp-turn/m 
Amplitude of electric fields of radiation, E0 = 1027 V/m  
Magnetice field of radition, H0 = 2.73 Amp-turn/m

Example 4, page 560

In [10]:
from numpy import pi
# electric and magnetic field
#given data :
r=2 # in m
mu0=4*pi*10**-7 
epsilon0=8.85*10**-12 
EbyH=sqrt(mu0/epsilon0) 
EH=1000/(4*r**2*pi**2) # in W/m**2
E=sqrt(EH*EbyH) 
H=(EH/E) 
print "Intensities of electric, E = %0.2f V/m" %E
print "Magnetic field of radiation, H = %0.4f Amp-turn/m  " %H

Intensities of electric, E = 48.85 V/m
Magnetic field of radiation, H = 0.1296 Amp-turn/m

Example 5, page 593

In [14]:
from math import degrees, pi, asin, sin, tan
# Degree of polarization
#given data :
thetai=45 # in degree
n=1.5 #/ index
thetar=asin(sin(thetai*pi/180)/n) # radian
thetar= degrees(thetar)
Rl=sin((thetai-thetar)*pi/180)**2/sin((thetai+thetar)*pi/180)**2 
Rp=tan(thetai-thetar*pi/180)**2/tan((thetai+thetar)*pi/180)**2 
D=((Rl-Rp)/(Rl+Rp))*100 
print "Degree of polarization, D = %0.2f %%" %D
# answer is wrong in the textbook

Degree of polarization, D = 49.44 %

Example 6, page 594

In [16]:
# Frequency
#given data :
Del=1 # in m
mu=4*pi*10**-7 # in H/m
sigma=4 # in siemen/m
v=1*10**-3/(pi*Del**2*mu*sigma) 
print "Frequency, v = %0.1f kHz " %v

Frequency, v = 63.3 kHz