Lecture 22, ACT 2

• Snapshots of a wave with angular frequency w are shown at 3 times:

  • Which of the following expressions describes this wave?

(a) y = sin(kx-wt)

(b) y = sin(kx+wt)

(c) y = cos(kx+wt)

• In what direction is this wave traveling?

(a) +x direction

(b) -x direction

• We claim this wave moves in the -x direction.

• The orange dot marks a point of constant phase.

• It clearly moves in the -x direction as time increases!!

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