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Question:

A progressive wave travelling along the positive x-direction is represented by y(x,t)=Asin(kx−ωt+φ). Its snapshot at t=0 is given in the figure: y(x,t)=Asin(kx−ωt+φ)

π/2

π

π/2

0

Solution:

y=Asin(kx−wt+φ) at x=0, t=0, y=0 and slope is negative ⇒ φ=π