Malus' Law

The Malus' Law calculator computes the intensity of light based on the initial intensity and the angle between the light's initial polarization direction and the axis of the polarizer.

INSTRUCTIONS: Enter the following:

• (I₀) Initial Intensity
• (θ) angle the light's initial polarization direction and the axis of the polarizer

Intensity (I):  The calculator returns the intensity in Watts per square meter.

The Math / Science

Malus' Law says that when a perfect polarizer is placed in a polarized beam of light, the intensity, I, of the light that passes through is given by the following equation:

        I = I₀ • cos²θ_i

where:

• I = Intensity of light based on Malus' Law
• I₀ = Initial Intensity in W/m²
• θ_i = Angle between the light's initial polarization direction and the axis of the polarizer

References

The definition and formula are from Wikipedia (https://en.wikipedia.org/wiki/Polarizer).