Light Inverse Square Law Calculator

Inverse Square Law Formula:

\[ I = \frac{P}{4 \pi r^2} \]

Intensity (I):

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1. What is the Inverse Square Law?

The Inverse Square Law describes how light intensity diminishes with distance from a point source. It states that intensity is inversely proportional to the square of the distance from the source.

2. How Does the Calculator Work?

The calculator uses the Inverse Square Law formula:

\[ I = \frac{P}{4 \pi r^2} \]

Where:

\( I \) — Intensity (W/m²)
\( P \) — Power (W)
\( r \) — Distance from source (m)
\( \pi \) — Pi (~3.14159)

Explanation: The equation shows that doubling the distance from a light source reduces the intensity to 1/4 of its original value.

3. Importance of Light Intensity Calculation

Details: Understanding light intensity is crucial for lighting design, photography, radiation safety, and many scientific applications where precise illumination is needed.

4. Using the Calculator

Tips: Enter the light source's power in watts and the distance from the source in meters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Does this law apply to all light sources?
A: It applies perfectly to point sources and reasonably well to sources where the distance is much greater than the size of the source.

Q2: What are typical intensity values?
A: Full sunlight is about 1000 W/m², while a 60W bulb at 1m distance gives about 4.8 W/m².

Q3: How does this relate to photography?
A: It explains why moving a light source further away requires longer exposures or larger apertures.

Q4: Are there exceptions to this law?
A: Yes, for very large sources, collimated beams (like lasers), or in absorbing media, the relationship may differ.

Q5: Can this be used for sound too?
A: Yes, sound intensity also follows an inverse square law in free field conditions.