Malus' Law and Light Intensity

What does Malus' Law mathematically express?

What happens to the transmitted light intensity when the angle between the polarizer's axis and the light's polarization direction is 90°?

If the initial intensity of unpolarized light is $I_0$, the intensity after passing through an ideal polarizer is:

What is the effect of adding a second polarizer oriented at 90° to the first one?

A beam of polarized light passes through two ideal polarizers oriented at 30° and 60° relative to the initial polarization direction. What fraction of the initial intensity remains?

If unpolarized light passes through two polarizers oriented at 45° to each other, the transmitted intensity is:

A polarizer and analyzer are oriented at 37°. If the initial light intensity is 100 W/m², what is the transmitted intensity?

Polarized light passes through three polarizers. The first is aligned vertically, the second at 45°, and the third horizontally. What fraction of the light's intensity is transmitted?

Malus' Law

Malus' Law describes the intensity of transmitted light through a polarizer.

Polarization by Scattering

Not directly related to Malus' law, but a different phenomenon.

Intensity of Transmitted Light

The intensity of light transmitted through a polarizer is related to the angle between the polarizer's axis and the light's polarization direction.

Malus' Law Equation

Mathematically, transmitted intensity (I) is I = I₀ cos²θ where I₀ is the initial intensity and θ is the angle between the polarizer axis and the light's polarization direction.

Polarizer and 90° Angle

When the angle between the light's polarization and the polarizer's axis is 90°, the transmitted intensity is zero.

Unpolarized Light Through a Polarizer

An ideal polarizer reduces the intensity of unpolarized light to half its original value.

Multiple Polarizers

When light passes through multiple polarizers, the intensity is reduced.
The angle between polarizers significantly affects the transmitted intensity.
Multiple polarizers are in series. The intensity of the light is reduced at each stage. Mathematically, it's the product of the cosine squared of each angle.
If the second polarizer is at 90° to the first, no light is transmitted.

Example Calculations

Calculating fractions of the initial intensity remaining after passing through multiple polarizers requires understanding cosine squared relationship and applying the formula I = I₀ cos²θ for each polarizer.

Practical Applications

Malus' Law is essential in understanding and controlling polarized light.
Applications are found in many optical devices.

Incident Light Alignment with Polarizer

When the electric field of the incident light aligns with the polarizer’s axis, the transmitted intensity is maximized.

This quiz explores Malus' Law, which explains how the intensity of light changes as it passes through polarizers. It covers the fundamental equation of transmitted intensity and the effects of angle on light polarization. Test your understanding of light intensity concepts and the behavior of polarizers.