From what I understand, light generally effects wine in 2 ways that can be a problem. Infrared/heat from sunlight contributes to the oxidation of wine, and destroys delicate compounds/esters within the wine that give it bouquet and flavor. Also microbes that produce off-flavors are encouraged, that would normally not succeed in growing in a cool/dark atmosphere. Another way that wine can be damaged is with strong fluorescent light, where budding yeast cells are inhibited from growth due to the ultraviolet rays present, which reduces the quality/vigor of the fermentation. It is certainly OK, to inspect your wine with moderate incandescent light or even a flashlight to see how fermentation is progressing and also to inspect lees/deposits in your fermentaton vessel, and also to see how clear the wine is.