The Inverse Square Law
The relationship between light intensity and distance is not linear; it follows the inverse square law.
If you double the distance from a light source, how much does the light intensity drop?
What is The Inverse Square Law?
"The inverse square law states that the intensity of light is inversely proportional to the square of the distance from the source."
If the distance between a lamp and pondweed doubles, what happens to the light intensity reaching the pondweed?
Why is the inverse square law useful in photosynthesis experiments?
A lamp is moved three times further away from a plant. The light intensity becomes approximately:
Calculations
Light Intensity ∝ 1 / (distance)²
Doubling the distance (2x) reduces intensity to 1/4 (2² = 4).
Tripling the distance (3x) reduces intensity to 1/9 (3² = 9).
If distance increases, light intensity decreases significantly.
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