What is light A person can see clearly in a mirror as it is transparent. But the person cannot see through its walls, floors, doors, or wooden windows because they are opaque. In a dark room, everything appears invisible to the eyes as when light falls in a direction it is reflected and comes to the human eyes. So light is a type of energy that allows the eyes to see properly. During the day, the main form of light is the Sun and the second form of light is the glow of the light. Other frequent sources are fire, electric