Definition

An instruĀ­ment used to measure the EXTINCTION COEFFICIENT of transmission of light in water. It consists of a constant light source placed at a specific distance from a photocell. When placed in water, the electrical OUTPUT of the photocell is proportional to the amount of light striking the cell which, in turn, depends upon the transparency of the water. The instrument is calibrated to read 100 perĀ­cent light transmission in air.