Single-slit minima (a sin θ = nλ (minima n=1)

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a sin θ = nλ (minima n=1

What each symbol means

SymbolWhat it stands for
aWidth of single slit (m)
nOrder of minimum (non-zero integer for standard minima condition)
\thetaAngular position of diffraction minimum from central axis
\lambdaWavelength (m)

When to use this

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