# Chapter 20 Electromagnetic Waves¶

## Example 20.1 Page no 618¶

In [20]:
#Given
L=5.5*10**-7                            #m
c=3*10**8                               #m s**-1
u=1.5

#Calculation
V=c/L
T=L/c
v=c/u
L1=v*T

#Result
print"(a) The frequency is",round(V*10**-14,3),"10**8","MHz","and time period is",round(T*10**15,1),"10**-19","micro s"
print"(b) The wavelenght in glass is",round(L1*10**7,1),"10**-7","m"

(a) The frequency is 5.455 10**8 MHz and time period is 1.8 10**-19 micro s
(b) The wavelenght in glass is 3.7 10**-7 m


## Example 20.2 Page no 619¶

In [24]:
#Given
V=2*10**8                             #m s**-1
Ur=1.0
C=3*10**8

#Calculation
Er=(C**2)/(V**2*Ur)

#Result
print" The relative permittivity is",Er

 The relative permittivity is 2.25


## Example 20.3 Page no 619¶

In [35]:
#Given
C=3*10**8
V=10**8
E0=0.5

#Calculation
L=C/V
Bz=E0/C

#Result
print"(a) There is the positive direction of x-axis of propagation of electromagnetic waves"
print"(b) The wavelengh of the wave is",L,"m"
print"(c) The component of associated magnetic field is",round(Bz*10**9,0),"cos(2*math.pi*10**8(t-x/c))"

(a) There is the positive direction of x-axis of propagation of electromagnetic waves
(b) The wavelengh of the wave is 3 m
(c) The component of associated magnetic field is 2.0 cos(2*math.pi*10**8(t-x/c))


## Example 20.4 Page no 619¶

In [41]:
#Given
L=6*10**-3                           #m
E0=33                                #V m**-1
C=3.0*10**8

#Calculation
import math
W=(2*math.pi*C)/(L)
B=E0/C

#Result
print"Magnetic field is",B,"sin*math.pi*10**11(t-x/c)"

Magnetic field is 1.1e-07 sin*math.pi*10**11(t-x/c)


## Example 20.5 Page no 619¶

In [46]:
#Given
I=8
E0=8.85*10**-12
C=3*10**8

#Calculation
import math
e0=math.sqrt((2*I)/(E0*C))

#Result
print"The amplitude of the electric field is",round(e0,1),"N C**-1"

The amplitude of the electric field is 77.6 N C**-1


## Example 20.6 Page no 619¶

In [65]:
#Given
L=0.024                                    #m
k=5.9*10**-9
c=3*10**8

#Calculation
V=L/k
t=L/c

#Result
print"(i) The number of oscillation is",round(V*10**-6,3),"10**6","Hz"
print"(ii) The coherence time is",t,"s"

(i) The number of oscillation is 4.068 10**6 Hz
(ii) The coherence time is 8e-11 s