CBSE Class 10 Answered

n spectroscopy, optical density is the measure of absorbance, and is defined as the ratio of the intensity of light falling upon a material and the intensity transmitted, on the other hand mass density tells us that how much amount of mass is contained per unit volume. Light travells slowly in optically denser medium. An optically denser medium need not to have greater mass density for example kerosene has mass density less than water but it is optically denser than water.