Malus' law (I = I0 cos²θ)

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I = I0 cos²θ

What each symbol means

SymbolWhat it stands for
ITransmitted intensity after polariser/analyser (W/m²)
I_0Incident polarised intensity on analyser (W/m²)
\thetaAngle between transmission axes (rad or deg consistent)

When to use this

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