How to Find the Focal Point of a Parabola
A parabola is a curved shape that can be used to focus energy at a single point. With a parabolic cooker, for example, the sun's rays are reflected at a focal point. In order to use the parabolic cooker effectively, you need to know the location of the focal point in order to find the point at which the temperature will be the hottest. To find the focal point, you must first find the width and depth of the parabola.
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Instructions
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1
Measure the distance across the top of the parabola from one side to the other, and measure the depth of the parabola.
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2
Divide the distance across the parabola by two to find the radius. For example, if the parabola has a diameter of 26 inches, you would divide 26 by two to get a radius of 13 inches.
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3
Square the parabola radius. For example, if the parabola has a 13 inch radius, you would square 13 to get 169.
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4
Multiply the depth of the parabola by 4. For example, if the parabola was 5 inches deep, you would multiply 5 by 4 to get 20.
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5
Divide the Step 3 result by the Step 4 result to find the distance above the vertex where the focal point is located. In this example, you would divide 169 by 20 to find the focal point is 8.45 inches above the vertex.
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References
- Photo Credit parabole image by Christophe Fouquin from Fotolia.com
