About of the power of a light bulb is converted to visible radiation

PHYSICS · Multi-part · A Level · Physics · Waves · Waves

Problem

About 5%5\% of the power of a 100 W100\ \text{W} light bulb is converted to visible radiation. What is the average intensity of visible radiation? Assume that the radiation is emitted isotropically and neglect reflection. (a) At a distance of 1 m1\ \text{m} from the bulb? (b) At a distance of 10 m10\ \text{m} from the bulb?

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