Problem set 10, number 1

As light from the surface penetrates water, its intensity is diminished. In the clear waters of the
Caribbean, the intensity is decreased by 15 percent for every 3 meters of depth. Thus, the intensity will
have the form of a general exponential function.
(a) If the intensity of light at the water’s surface is Io , find a formula for I(d), the intensity of light at a
depth of d meters. Your formula should depend on Io and d.
(b) At what depth will the light intensity be decreased to 1% of its surface intensity?