When light strikes the surface of a medium such as water or glass, its intensity decreases with depth. TheBeer-Lambert-Bouguer lawstates that the percentage of decrease is the same for each additional unit of depth. In a certain lake, intensity decreases about85%for each additional meter of depth.

Use a formula to express intensityIas an exponential function ofd. (UseI₀to denote the initial intensity.)

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At what depth will the intensity of light bethree-tenths of the intensity of light striking the surface? (Round your answer to two decimal places.)

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