I'm studying topic of phase velocity and group velocity. For different values of (w) and (k), I'm obtaining same group velocity as 1 but different wave pattern. I need help for Q2) in inferences and bit theory behind it.
Transcribed Image Text: w- S.Thoushik 21MIS1058 Phase abd group velocity
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Phase and Group velocity of EM waves
Tools required:
http://demonstrations.wolfram.com/GroupAndPhaseVelocity/
Objective:
To understand the nature of EM waves travelling in a medium with the help of Phase and
Group velocities.
Theory: Any real signal consists of travelling-waves of many different frequencies, which
travel together as a group, at a speed that will always be less than or equal to the speed of
light in vacuum. To gain some in Bold into what may happen when a real signal travels
through a dispersive medium, we consider adding two waves of equal amplitude. When two
travelling
waves with unit amplitude fi(z.t) = cos(kz-mit) and f(z,t) = cos(k2z-@²t) are added, we get
fi(z.t) + f,(z,t)= cos(k,z– 0,t) + cos(k,z – 0,t)
Ak
= 2 cos
2
Δω
t cos(k · z
2
(1-0 – 2
Ak k, - k,
k + k,
k =
W, + W2
Δω ωω
2
Where,
2
2
and
The result is a fast oscillating wave that travels with a phase velocity
k
and the
Δω
YV )
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