The physical and optical properties of cometary dust grains are of great interest at least for two reasons: i) these grains are responsible for much of the light scattered from cometary coma and dust tail; hence grain optics influences the basic appearances of comets;
ii) the grains may be unprocessed relics from the time of formation of the solar system or before, hence study of cometary grains is very important to investigate physical conditions that exited in the beginning of the formation of solar system. This information is imprinted in the cometary dust grains. There are several ways that the cometary dust can be studied - in situ measurements using space experiments, ground based observations etc. As space based experiments are expensive and comets show differing properties, ground
based studies of comets are very relevant. Photopolarimetry of the coma of comets serves as an important tool to study cometary dust. The talk will focus on a brief overview of comet study and its contribution to basic sciences. Apart from this, we have studied several comets using polarization and photometric methods. Characteristics of the cometary
grains as revealed from photometric and polarimetric observations at low phase angle along with the opposition effects based on the study of comet C/2007 N3 (Lulin) by us in recent times will be discussed.