Rayleigh criterion (circular aperture) (θ ≈ 1.22 λ/D)

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θ ≈ 1.22 λ/D

What each symbol means

SymbolWhat it stands for
DDiameter of circular aperture (m)
\thetaMinimum angular resolution (Rayleigh, rad)
\lambdaWavelength (m)

When to use this

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