1. What is Malus' Law?

Malus' Law describes the intensity of polarized light after passing through a polarizing filter. It states that the intensity of light transmitted through a polarizer is proportional to the square of the cosine of the angle between the light's initial polarization direction and the polarizer's axis.

2. How Does the Calculator Work?

The calculator uses Malus' Law equation:

Where:

• \( I \) — Transmitted intensity (W/m²)
• \( I_0 \) — Initial intensity (W/m²)
• \( \theta \) — Angle between polarization directions (degrees)

Explanation: When θ = 0°, all light passes through (I = I₀). When θ = 90°, no light passes through (I = 0).

3. Applications of Malus' Law

Details: Malus' Law is fundamental in optics, used in polarimeters, LCD displays, photography filters, and optical communication systems.

4. Using the Calculator

Tips: Enter initial intensity in W/m² and angle in degrees (0-90). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is the intensity proportional to cos²θ rather than just cosθ?
A: The electric field is proportional to cosθ, but intensity is proportional to the square of the electric field amplitude.

Q2: Does Malus' Law apply to unpolarized light?
A: No, Malus' Law specifically describes polarized light. For unpolarized light, a polarizer reduces intensity by 50% regardless of orientation.

Q3: What happens at angles between 0° and 90°?
A: The transmitted intensity gradually decreases from maximum to zero as the angle increases.

Q4: Can Malus' Law be used for multiple polarizers?
A: Yes, for multiple polarizers, you apply the law sequentially for each polarizer.

Q5: What are typical units for light intensity?
A: The SI unit is watts per square meter (W/m²), though other units like lux or foot-candles may be used in specific applications.