Reflection and Refraction Maxwell's equations lead to definition for ...

Interference can result from difference in pathlengthIf the waves initially start out with same phase, the difference inphase, δ, due to different paths iswhereδ = (φ 1 − φ 2 )= 2π ⋅x 1− 2π⋅x 2λ λ2π(x 1 − x 2 )λx 1and x 2are the lengths to the measurement point from source2π/λ is the number of a complete waves per unit lengthThus, when δ = 0, 2π... (an integral number of wavelengths)m ⋅2π = 2π(x 1 − x 2 )λm⋅λ = δ constructive interference2πwhen δ = π, 3π... (an integral number of wavelengths+1/2)⎛ 2m +1⎞⎝ 2 ⎠ λ = δ2πdestructive interferenceCEM 835 page 3-11