Phase from path difference (Δφ = (2π/λ)Δx)

jee-mainjee-advancedneet-ug

Δφ = (2π/λ)Δx

What each symbol means

SymbolWhat it stands for
\lambdaWavelength in medium (m)
\Delta xPath difference (m)
\Delta\phiPhase difference between two waves (rad)

When to use this

Standard JEE / NCERT assumptions unless stated (paraxial, thin lens, coherent YDSE sources, etc.).