A photocolorimeter is a scientific instrument used to measure the intensity of light. It is also known as spectrophotometer and colorimeter. The term spectrophotometer is often used to describe instruments that measure the absorption of light by a sample, whereas a colorimeter is used to measure the concentration of a colored solution. Another synonym for photocolorimeter is photometer, which is an instrument for measuring the intensity of light in a specific area. Additionally, a radiometer is also a synonym for photocolorimeter, which measures the power of electromagnetic radiation in the ultraviolet, visible, and infrared regions of the spectrum. Despite having different names, these instruments are all used to measure the intensity of light and electromagnetic radiation.