In terms of spectrophotometer, we need to make the light monochromatic before passing it to sample. For that, we use diffraction grating. From the research, I found out that the grating reflects light into different wavelengths. Also, the grating moves in such a way that each wavelength has an opportunity to pass through slit to sample. According to one journal, the monochromatic light is needed to make sure every photon has same energy and wavelength, which means everyone of them, has an equal opportunity to hit the particle. Is there better explanation in this theory? Also, Am I right in thinking that all wavelengths scattered from grating will hit the particles but particles will only absorb certain wavelength?
From wikipedia: "spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength". The measurement consists of applying a specific wavelength (selected by the grating and slit) and measuring the transmission (or reflection) from the sample. By scanning the grating angle, we scan through the wavelengths and can then plot the dependence vs. wavelength. If we did not send a single wavelength at a time, we would not get a measurement than can be simply interpreted as transmission vs. wavelength.