
Concept explainers
The light from a lightbulb radiates outward in all directions.
a. Consider the interior of an imaginary sphere on which the light shines. The surface area of the sphere is directly proportional to the square of the radius. If the surface area of a sphere with a 10-m radius is
b. Explain how the surf ace area changed when the radius of the sphere increased from 10 m to 20 m.
c. Based on your answer from part (b) how would you expect the intensity of light to change from a point 10 m from the lightbulb to a point 20 m from the lightbulb?
d. The intensity of light from a light source varies inversely as the square of the distance from the source. If the intensity of a lightbulb is 200

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