Physics

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Malus Law Calculator.

Calculate ideal polarized-light transmission through an analyzer.

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Set your values

Results update as you type.

02 / ANSWER

Incident intensity

Polarizer angle

Transmitted intensity

0.000000W/m²

Results update automatically as you type.

Use Cases

Optics Lab Experiments

Quickly verify Malus's Law in a teaching lab by comparing measured transmitted intensities with theoretical values for various analyzer angles.

Example: Set incident intensity to 100 W/m² and angle to 30° to get 75 W/m².

Designing Polarized Light Systems

Engineers can estimate light loss through polarizing filters in optical systems, such as cameras or sensors, to optimize performance.

Example: Check transmission at 45° to see 50% intensity reduction.

Frequently Asked Questions

What is Malus's Law?: Malus's Law states that when polarized light passes through an analyzer, the transmitted intensity I equals the incident intensity I₀ times the square of the cosine of the angle θ between the polarizer and analyzer: I = I₀ cos²θ. This calculator applies that formula.
What units should I use for incident intensity?: Enter the incident intensity in watts per square meter (W/m²). The calculator will output the transmitted intensity in the same unit, W/m².
What does the polarizer angle represent?: The polarizer angle is the angle in degrees between the transmission axis of the polarizer and the analyzer. It determines how much of the polarized light passes through, with 0° giving full transmission and 90° giving zero.

Tips & Common Mistakes

Tips

Ensure the incident light is fully polarized before using Malus's Law; otherwise, results may not match reality.
Use angles between 0° and 90° for typical scenarios; angles outside this range give the same result as their equivalent within it.
Remember that the calculator assumes ideal conditions—real polarizers may have slight absorption losses.
Double-check that your intensity is in W/m²; other units will give incorrect results.

Common Mistakes to Avoid

Forgetting to convert the angle to radians when doing manual calculations—this calculator handles degrees for you.
Using the angle between the incident light's polarization direction and the analyzer, but the formula requires the angle between the polarizer and analyzer axes.
Assuming the transmitted intensity is linear with angle; it actually follows a cosine-squared relationship.

Last updated: August 13, 2026

Use Cases

Optics Lab Experiments

Quickly verify Malus's Law in a teaching lab by comparing measured transmitted intensities with theoretical values for various analyzer angles.

Example: Set incident intensity to 100 W/m² and angle to 30° to get 75 W/m².

Designing Polarized Light Systems

Engineers can estimate light loss through polarizing filters in optical systems, such as cameras or sensors, to optimize performance.

Example: Check transmission at 45° to see 50% intensity reduction.

Frequently Asked Questions

What is Malus's Law?

Malus's Law states that when polarized light passes through an analyzer, the transmitted intensity I equals the incident intensity I₀ times the square of the cosine of the angle θ between the polarizer and analyzer: I = I₀ cos²θ. This calculator applies that formula.

What units should I use for incident intensity?

Enter the incident intensity in watts per square meter (W/m²). The calculator will output the transmitted intensity in the same unit, W/m².

What does the polarizer angle represent?

The polarizer angle is the angle in degrees between the transmission axis of the polarizer and the analyzer. It determines how much of the polarized light passes through, with 0° giving full transmission and 90° giving zero.

Tips & Common Mistakes

Tips

Ensure the incident light is fully polarized before using Malus's Law; otherwise, results may not match reality.
Use angles between 0° and 90° for typical scenarios; angles outside this range give the same result as their equivalent within it.
Remember that the calculator assumes ideal conditions—real polarizers may have slight absorption losses.
Double-check that your intensity is in W/m²; other units will give incorrect results.

Common Mistakes to Avoid

Forgetting to convert the angle to radians when doing manual calculations—this calculator handles degrees for you.
Using the angle between the incident light's polarization direction and the analyzer, but the formula requires the angle between the polarizer and analyzer axes.
Assuming the transmitted intensity is linear with angle; it actually follows a cosine-squared relationship.

Use Cases

Optics Lab Experiments

Quickly verify Malus's Law in a teaching lab by comparing measured transmitted intensities with theoretical values for various analyzer angles.

Example: Set incident intensity to 100 W/m² and angle to 30° to get 75 W/m².

Designing Polarized Light Systems

Engineers can estimate light loss through polarizing filters in optical systems, such as cameras or sensors, to optimize performance.

Example: Check transmission at 45° to see 50% intensity reduction.

Frequently Asked Questions

What is Malus's Law?

What units should I use for incident intensity?

Enter the incident intensity in watts per square meter (W/m²). The calculator will output the transmitted intensity in the same unit, W/m².

What does the polarizer angle represent?

Tips & Common Mistakes

Tips

Ensure the incident light is fully polarized before using Malus's Law; otherwise, results may not match reality.
Use angles between 0° and 90° for typical scenarios; angles outside this range give the same result as their equivalent within it.
Remember that the calculator assumes ideal conditions—real polarizers may have slight absorption losses.
Double-check that your intensity is in W/m²; other units will give incorrect results.

Common Mistakes to Avoid

Forgetting to convert the angle to radians when doing manual calculations—this calculator handles degrees for you.
Using the angle between the incident light's polarization direction and the analyzer, but the formula requires the angle between the polarizer and analyzer axes.
Assuming the transmitted intensity is linear with angle; it actually follows a cosine-squared relationship.