8 24.1 Light waves and the coherent condition of waves ifA1≠A2then p=2nz,A=A1+A2(n=0,1,2,…) 4=(2n+1)z,A=4-42|(n=0,12,…) 里(14c0-a+= >Case 2 Y,(r, t)=A cos(kr -at+o) y(r,t)=y1(r,t)+y2(r,) A, cos(kr -at+o)+A cos(hr -at+o) s24.1 Light waves and the coherent condition of waves (kr, -at+o)+(kr, -at+o) y(r, t)=2A cos[ 2 cos[ (kr-at+o)-(k 2-+ 2 A, coS( )cos(r2+r1)-at+小l P(r, t)=2A, cos (2-G)cosl(r+2)-at+pI 2 Path difference The total amplitude k depends on (F2-r1 △r 66 if A1 ≠ A2 then (2 1) , ( 0,1,2, ) 2 , ( 0,1,2, ) 1 2 1 2 L L = + = − = = = + = n A A A n n A A A n ∆φ π ∆φ π cos( ) cos( ) ( , ) ( , ) ( , ) 1 1 1 2 1 2 = −ω + φ + −ω + φ = + A kr t A kr t Ψ r t Ψ r t Ψ r t ¾Case 2 ( , ) cos( ) ( , ) cos( ) 2 1 2 1 1 1 ω φ ω φ Ψ = − + Ψ = − + r t A kr t r t A kr t o2 r2 r1 p o1 §24.1 Light waves and the coherent condition of waves ( ) ] 2 )cos[ 2 2 cos( ] 2 ( ) ( ) cos[ ] 2 ( ) ( ) ( , ) 2 cos[ 2 1 2 1 1 1 2 1 2 1 ω φ ω φ ω φ ω φ ω φ + − + − = − + − − + ⋅ − + + − + = r r t kr kr k A kr t kr t kr t kr t Ψ r t A ( ) ] 2 ( ) cos[ 2 ( , ) 2 cos = 1 2 − 1 r1 + r2 −ωt + φ k r r k Ψ r t A r r r k − = ∆ λ π ( ) 2 2 1 The total amplitude depends on §24.1 Light waves and the coherent condition of waves Path difference