Answer :

Final answer:

The Inverse Square Law for Light indicates that when the distance from a light source doubles, the intensity of the light is reduced to one-quarter of its original value. Hence, a 120-W lightbulb with an intensity of 2.4 W/m² at 2 m will have an intensity of 0.6 W/m² at 4 m.

Explanation:

The question relates to the intensity of light and how it changes with distance, which involves the Inverse Square Law for Light. The original intensity of a 120-W lightbulb measured at a distance of 2 m is 2.4 W/m². According to the Inverse Square Law, when the distance is doubled, the intensity of light is affected by the square of the change in distance. Therefore, the new intensity will be ¼ of the original intensity because the distance has been doubled (½) and then squared (½)² equals ¼.

If the distance from the light source increases from 2 m to 4 m, the height or distance from the light source effectively quadruples the area over which the light spreads. So, the new intensity at 4 m away would be 0.6 W/m², which is one-quarter of the original intensity at 2 m. This principle can be applied in various scenarios involving light emission and intensity, such as in lighting design and in analyzing the brightness of celestial objects.

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