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Inverse Square Law: How Does Distance Affect the Spreading of Light? (page 2)

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Author: Alex Jacobsen

Why?

When light encounters the edge of something it will bend around that edge, much like ripples of water hitting a pier. This is known as diffraction. When the obstruction (our paper) is close to the focal plane—or where the shadow is being cast—the light doesn’t have much of a chance to bend, and the shadow looks much like the shape in the paper. When the paper is farther away, the light has more time to bend, and the shape starts to change more into an image of what is behind the paper (in this case, the sun). The reason that all the shapes look the same when they’re far away from the ground is because the bending of the light smears out all the angles and lines of the shapes.

So why did your shapes start to look dimmer as they became bigger? Distance affects the spreading of light according to the inverse square law of light. This law basically states that as the source of light gets farther away from any surface the light is projected onto, the intensity of light per square centimeter decreases. Remember, only so many rays of light can make it through each hole you cut into your construction paper. When these rays get spread out, the image gets bigger, but won’t be as bright!

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