§122。ne- dimensional waves and the equation of waves Choose a ray of wave as x axis, construct a one-dimensional coordinate system. O is the origin, v is the velocity along the tx direction. Method 1 P(r) ifY0=Acos(ot+φ) The propagating time of the、△ state from point o to point P(c) The phase of point P(r)at instant t is the same as the point o at instant t-4t 812.2 one-dimensional waves and the equation of waves therefore Yn(x,)=0(0,t-△)=Acoo(t-)+外 (x,D)= Acosta(-1)+y(1) Method 2: L P The phase difference between two points of space interval of n is 2T. The phase at point P lag .2 relative to point o 88 Method 1 if cos( ) Ψ0 = A ωt + φ′ v O P(x) x The propagating time of the state from point o to point P(x) v x ∆t = Choose a ray of wave as x axis, construct a one-dimensional coordinate system. O is the origin, v is the velocity along the +x direction. The phase of point P(x) at instant t is the same as the point o at instant t-∆t. §12.2 one-dimensional waves and the equation of waves ( , ) = cos[ω( − t) +φ] v x Ψ x t A (1) ( , ) (0, ) 0 Ψ x t Ψ t t p = − ∆ = cos[ω( − ) +φ′] v x A t therefore u O P(x) x Method 2: The phase at point P lag relative to point o π λ ⋅ 2 x The phase difference between two points of space interval of λ is 2π. §12.2 one-dimensional waves and the equation of waves