What kinds of images are made by painting or drawing on top of the surface of a rock?

Rohit is trying to tune an instrument

When a vertical beam of light passes through a transparent medium, the rate at which its intensity i decreases is proportional to i(t), where t represents the thickness of the medium (in feet). in clear seawater, the intensity 3 feet below the surface is 25% of the initial intensity i0 of the incident beam. what is the intensity of the beam "10" feet below the surface? (give your answer in terms of i0. round any constants or coefficients to five decimal places.)

Efficiency is the ratio of to for a system a)power in to power in b)power in to power out c) power out to power out d) power out to power in