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Re: [Phys-L] phase of a classical wave function



-> -----Original Message-----
-> From: Phys-l [mailto:phys-l-bounces@www.phys-l.org] On Behalf Of John
-> Denker
-> Sent: Wednesday, January 21, 2015 12:16 PM
-> To: Phys-L@Phys-L.org
-> Subject: Re: [Phys-L] phase of a classical wavefunction
-> One way to stay out of trouble when dealing with "phase"
-> issues is to switch to the /phasor/ representation:
->
-> ψR(x,t) = a1 sin( kx - ωt) + a2 cos( kx - ωt) [1]
->
-> ψL(x,t) = b1 sin(-kx - ωt) + b2 cos(-kx - ωt) [2]
->
-> The phase angle does not appear directly in these equations ... although you
-> can compute it in terms of atan2(a1, a2) if desired.

Another advantage is that it answers the question "Should I use sine or cosine when describing waves?" BOTH! It also forces students to pay attention to initial conditions.

Aside: EEs like to infer cosine when writing their "phasors" e.g. V= 2.5/__15___ means 2.5 cos(ωt[radians] + 15 [degrees]) Gag! (Ref: Hayt and Kemmerly)