Visibility in water is something of great interest to scuba divers. The amount of light reaching a given depth depends on several factors. The most important factors are the light absorption of the water and the intensity of the original light source (which is above the water—for a scuba diver this would normally be sunlight). If we reformulate the problem as that of determining the proportion of the original light reaching a given depth, then the intensity of the original light source drops out of the problem.
The proportion, p, of light reaching a depth, , through water with absorption coefficient is given by . Typical values for the coefficient for water are in the range , with smaller values representing clearer water and larger values indicating more opaque water.
Using the sliders, select the values of and . The diagram shows the depth, , to which the proportion of source light reaches through water with absorption coefficient .