Wave phenomena Flashcards
What are the three types of waves?
Mechanical e.g. Sound waves and waves at sea
Electromagnetic
Matter e.g. Light and infrared
What is the wavenumber?
k =2π/λ
What is the wavefunction U(x,t)?
U(x,t)=Acos(kx±ωt)
The sign is + if the wave is left travelling
The sign is - if the wave is right travelling
U(x, t) = Aexp(i(kx±ωt))
What is the angular frequency?
ω =2π/T= 2πf
What is the wavespeed?
c =λ/T= fλ =ω/k
What is a transverse wave?
A wave for which its motion is perpendicular to the direction of travel
What is a longitudinal wave?
A wave for which its motion is parallel to the direction of travel
What is the wave eqaution?
∂^2U(x, t)∂t^2=c^2∂^2U(x, t)∂x^2
With c=ω/k=fλ
What is the principle of superposition?
The summation of two or more waves with potentially different f,λ,c
What is the phase of a wave?
The argument, kx-ωt
U(x, t) = Acos(kx − ωt + ϕ)
What is destructive inetrference?
When waves are out of phase and cancel out
What is constructive interference?
When waves are in phase and their amplitudes sum to a maximum
What is the phase velocity?
v_p=ω/k
What is the group velocity?
v_g=dω/dk
What is dispersion?
When the phase speed varies with wavelength or v_g does not equal v_p
