spectrophotometry is the science of measuring the light-absorbing and light-transmitting characteristics of a substance. Many substance absorb light and transmit light of specific wavelengths within the ultraviolet (200-400)ม visible (400-700) and near-infrared (700-1000) regions of the electromagnetic spectrum These light-absorbing/light-transmitting characteristics of a substance are useful in determining the presence and concentration of that substance in a sample
the instument used to measure the amount of light of a specific wavelength absorbed or transmitted by a substance is called a spectrophotometer in a spectrophotometer a sample of the substance is placed across the path of a light beam of a chosen specific wavelength the spectrophotometer determines the intensity of the light entering the sample and the intensity of the light leaving the sample then calculates the amount of light transmitted and absorbed by the substance