The monochromator itself houses the mirrors, slits, and grating. In this volume, we will describe the monochromator, an important part of the spectrophotometer that was explained in UV TALK LETTER Vol. A. The principle of measurement for UV-Visible Spectroscopy or UV-Visible spectrophotometer is relatively straightforward and consists of a light source, a wavelength dispersive element, sample, and detector. It explains how these instruments measure light intensity across various wavelengths and highlights the. HOLMARC's Spectra UV-VIS-INR standard monochromators are designed for general spectroscopic research needs.