👉 A spectrophotograph is a type of light intensity meter that measures the absorbance or luminous flux of a substance. It uses a spectrometer to measure the concentration of a specific chemical compound or mixture in an analyte, such as water, and then converts this concentration into a visible image on a photographic plate. The absorbance measurement is done by measuring the ratio of the incident light intensity to the absorbed light intensity, which can be converted into luminous flux (L) using a standard