1. What is a Light Intensity Calculator?

Definition: This calculator determines the light intensity from an isotropic source based on luminous flux and distance.

Purpose: It helps lighting designers, engineers, and photographers calculate how light intensity diminishes with distance from the source.

2. How Does the Calculator Work?

The calculator uses the inverse square law formula:

Where:

• \( I \) — Light intensity (candela, cd)
• \( P \) — Luminous flux (lumens)
• \( d \) — Distance from source (meters)

Explanation: The luminous flux is spread over a spherical surface area (4πd²) at distance d from the isotropic point source.

3. Importance of Light Intensity Calculation

Details: Proper intensity calculation ensures adequate illumination for tasks, safety in work environments, and desired lighting effects.

4. Using the Calculator

Tips: Enter the luminous flux in lumens and distance in meters. Both values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is an isotropic light source?
A: A theoretical point source that emits light equally in all directions.

Q2: How does distance affect light intensity?
A: Intensity follows the inverse square law - it decreases with the square of the distance from the source.

Q3: What's a typical luminous flux for common light bulbs?
A: 60W incandescent ≈ 800 lumens, 100W ≈ 1600 lumens, LED equivalents use less power for similar output.

Q4: When would this calculation not apply?
A: For directional light sources (like lasers or spotlights) or in media that absorb/scatter light.

Q5: How is this related to illuminance (lux)?
A: Illuminance (lux) = Intensity (cd) / distance² (m²) for perpendicular surfaces.