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• The two waves f and g propagate without distortion
• The spatial form of f and g is determined by initial conditions and by
boundary conditions
While the waves propagate at (constant) velocity c
0
, the material particles move
at velocity:
∂u ∂f ∂f( x−c0t)
vxt ( , ) = =− c0 =−cf′ 0
( x−ct 0
) with f′
( x−ct
0
)
∂t ∂t ∂( x−c0t)
But since:
we have:
∂u
σ( x, t) = Eε
= E = Ef′
( x−c0t)
∂x
vxt
c
E σ
0
( , ) =− ( xt , )
3