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Inverse Square Law

Intensity from a point source decreases with the square of distance: I₂/I₁ = (d₁/d₂)². Applies to light, sound, gravity, electric fields, and radiation. Doubling distance quarters intensity.

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I₂/I₁ = (d₁/d₂)² for any point source Doubling distance quarters intensity Point source: I = P/(4πd²) ΔdB = 20log(d₁/d₂) for intensity

Key quantities
I₂/I₁ = (d₁/d₂)²
Intensity Ratio
Key relation
I = P/(4πd²)
Point Source
Key relation
ΔdB = 20log(d₁/d₂)
Decibel Change
Key relation
d₂ = d₁√(I₁/I₂)
Distance Factor
Key relation

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Why: The inverse square law governs how light, sound, gravity, and radiation spread from point sources. Essential for lighting design, acoustic planning, and radiation safety.

How: Intensity decreases as 1/d² because the same power spreads over a sphere of area 4πd². For two distances: I₂/I₁ = (d₁/d₂)². Decibel change: ΔdB = 20log₁₀(d₁/d₂).

I₂/I₁ = (d₁/d₂)² for any point sourceDoubling distance quarters intensity
Sources:NIST Physical ConstantsMIT OpenCourseWare Physics

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Solve Inverse Square LawEnter reference and target distances

💡 Light Intensity from Lamp

LED lamp with 1000 lux at 1 meter, calculate intensity at 3 meters

🔊 Sound Level from Speaker

Speaker producing 0.1 W/m² at 1 meter, find intensity at 5 meters

🌍 Gravitational Force

Gravitational force between Earth and Moon at different distances

⚡ Electric Field Strength

Electric field from point charge: 1000 N/C at 1 m, find at 2 m

☢️ Radiation Dose Rate

Radiation source: 0.01 mSv/h at 1 m, calculate safe distance for 0.001 mSv/h

Input Parameters

lux
m
m
lux
W
Intensity at reference distance must be greater than 0

For educational and informational purposes only. Verify with a qualified professional.

🔬 Physics Facts

📏

I₂/I₁ = (d₁/d₂)²; intensity falls inversely with distance squared

— Classical Physics

💡

Point source: I = P/(4πd²) where P is total power

— Radiometry

📊

ΔdB = 20log₁₀(d₁/d₂) for intensity in decibels

— Acoustics

📐

Distance for desired intensity: d₂ = d₁√(I₁/I₂)

— Inverse Square Law

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